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  • 1.
    Ahmadi, Sareh
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Agnarsson, Björn
    Bidermane, Ieva
    Wojek, Bastian M.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Noël, Quentin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Sun, Chenghua
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Site-dependent charge transfer at the Pt(111)-ZnPc interface and the effect of iodine2014Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, nr 17, s. 174702-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electronic structure of ZnPc, from sub-monolayers to thick films, on bare and iodated Pt(111) is studied by means of X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and scanning tunneling microscopy. Our results suggest that at low coverage ZnPc lies almost parallel to the Pt(111) substrate, in a non-planar configuration induced by Zn-Pt attraction, leading to an inhomogeneous charge distribution within the molecule and an inhomogeneous charge transfer to the molecule. ZnPc does not form a complete monolayer on the Pt surface, due to a surface-mediated intermolecular repulsion. At higher coverage ZnPc adopts a tilted geometry, due to a reduced molecule-substrate interaction. Our photoemission results illustrate that ZnPc is practically decoupled from Pt, already from the second layer. Pre-deposition of iodine on Pt hinders the Zn-Pt attraction, leading to a non-distorted first layer ZnPc in contact with Pt(111)-I(root 3x root 3) or Pt(111)-I(root 7x root 7), and a more homogeneous charge distribution and charge transfer at the interface. On increased ZnPc thickness iodine is dissolved in the organic film where it acts as an electron acceptor dopant.

  • 2.
    Ahmadi, Sareh
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Shariati, M. Nina
    Yu, Shun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Molecular layers of ZnPc and FePc on Au(111) surface: Charge transfer and chemical interaction2012Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, nr 8, s. 084705-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have studied zinc phthalocyanine (ZnPc) and iron phthalocyanine (FePc) thick films and monolayers on Au(111) using photoelectron spectroscopy and x-ray absorption spectroscopy. Both molecules are adsorbed flat on the surface at monolayer. ZnPc keeps this orientation in all investigated coverages, whereas FePc molecules stand up in the thick film. The stronger inter-molecular interaction of FePc molecules leads to change of orientation, as well as higher conductivity in FePc layer in comparison with ZnPc, which is reflected in thickness-dependent differences in core-level shifts. Work function changes indicate that both molecules donate charge to Au; through the pi-system. However, the Fe3d derived lowest unoccupied molecular orbital receives charge from the substrate when forming an interface state at the Fermi level. Thus, the central atom plays an important role in mediating the charge, but the charge transfer as a whole is a balance between the two different charge transfer channels; pi-system and the central atom.

  • 3.
    Ahmadzadeh, Karan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Scott, Mikael
    Ruprecht Karls Univ Heidelberg, Interdisciplinary Ctr Sci Comp, Neuenheimer Feld 205, D-69120 Heidelberg, Germany..
    Brand, Manuel
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Vahtras, Olav
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Li, Xin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Rinkevicius, Zilvinas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Kaunas Univ Technol, Fac Math & Nat Sci, Dept Phys, LT-51368 Kaunas, Lithuania..
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Efficient implementation of isotropic cubic response functions for two-photon absorption cross sections within the self-consistent field approximation2021Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 154, nr 2, artikel-id 024111Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Within the self-consistent field approximation, computationally tractable expressions for the isotropic second-order hyperpolarizability have been derived and implemented for the calculation of two-photon absorption cross sections. The novel tensor average formulation presented in this work allows for the evaluation of isotropic damped cubic response functions using only similar to 3.3% (one-photon off-resonance regions) and similar to 10% (one-photon resonance regions) of the number of auxiliary Fock matrices required when explicitly calculating all the needed individual tensor components. Numerical examples of the two-photon absorption cross section in the one-photon off-resonance and resonance regions are provided for alanine-tryptophan and 2,5-dibromo-1,4-bis(2-(4-diphenylaminophenyl)vinyl)-benzene. Furthermore, a benchmark set of 22 additional small- and medium-sized organic molecules is considered. In all these calculations, a quantitative assessment is made of the reduced and approximate forms of the cubic response function in the one-photon off-resonance regions and results demonstrate a relative error of less than similar to 5% when using the reduced expression as compared to the full form of the isotropic cubic response function.

  • 4.
    Ai, Yue-Jie
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Zhang, Feng
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Cui, Gang-Long
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Fang, Wei-Hai
    Ultrafast deactivation processes in the 2-aminopyridine dimer and the adenine-thymine base pair: Similarities and differences2010Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 133, nr 6, s. 064302-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    2-aminopyridine dimer has frequently been used as a model system for studying photochemistry of DNA base pairs. We examine here the relevance of 2-aminopyridine dimer for a Watson-Crick adenine-thymine base pair by studying UV-light induced photodynamics along two main hydrogen bridges after the excitation to the localized (1)pi pi(*) excited-state. The respective two-dimensional potential-energy surfaces have been determined by time-dependent density functional theory with Coulomb-attenuated hybrid exchange-correlation functional (CAM-B3LYP). Different mechanistic aspects of the deactivation pathway have been analyzed and compared in detail for both systems, while the related reaction rates have also be obtained from Monte Carlo kinetic simulations. The limitations of the 2-aminopyridine dimer as a model system for the adenine-thymine base pair are discussed. (C) 2010 American Institute of Physics. [doi:10.1063/1.3464485]

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  • 5.
    Alfredsson, Y.
    et al.
    Department of Physics, Uppsala University.
    Brena, Barbara
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Nilson, K.
    Department of Physics, Uppsala University.
    Åhlund, J.
    Department of Physics, Uppsala University.
    Kjeldgaard, L.
    MAX-lab, University of Lund.
    Nyberg, Mats
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Mårtensson, N.
    Department of Physics, Uppsala University.
    Sandell, A.
    Department of Physics, Uppsala University.
    Puglia, C.
    Department of Physics, Uppsala University.
    Siegbahn, H.
    Department of Physics, Uppsala University.
    Electronic structure of a vapor-deposited metal-free phthalocyanine thin film2005Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 122, nr 21Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electronic structure of a vapor-sublimated thin film of metal-free phthalocyanine (H2Pc) is studied experimentally and theoretically. An atom-specific picture of the occupied and unoccupied electronic states is obtained using x-ray-absorption spectroscopy (XAS), core- and valence-level x-ray photoelectron spectroscopy (XPS), and density-functional theory (DFT) calculations. The DFT calculations allow for an identification of the contributions from individual nitrogen atoms to the experimental N1s XAS and valence XPS spectra. This comprehensive study of metal-free phthalocyanine is relevant for the application of such molecules in molecular electronics and provides a solid foundation for identifying modifications in the electronic structure induced by various substituent groups.

  • 6. Al-Khalili, A
    et al.
    Thomas, R
    Ehlerding, A
    Hellberg, F
    Geppert, W D
    Zhaunerchyk, V
    af Ugglas, M
    Larsson, M
    Uggerud, E
    Vedde, J
    Adlhart, C
    Semaniak, J
    Kaminska, M
    Zubarev, R A
    Kjeldsen, F
    Andersson, P U
    Österdahl, Fabian
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Bednarska, V A
    Paal, A
    Dissociative recombination cross section and branching ratios of protonated dimethyl disulfide and N-methylacetamide2004Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 121, nr 12, s. 5700-5708Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dimethyl disulfide (DMDS) and N-methylacetamide are two first choice model systems that represent the disulfide bridge bonding and the peptide bonding in proteins. These molecules are therefore suitable for investigation of the mechanisms involved when proteins fragment under electron capture dissociation (ECD). The dissociative recombination cross sections for both protonated DMDS and protonated N-methylacetamide were determined at electron energies ranging from 0.001 to 0.3 eV. Also, the branching ratios at 0 eV center-of-mass collision energy were determined. The present results give support for the indirect mechanism of ECD, where free hydrogen atoms produced in the initial fragmentation step induce further decomposition. We suggest that both indirect and direct dissociations play a role in ECD.

  • 7. Amft, Martin
    et al.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Skorodumova, Natalia V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Influence of the cluster dimensionality on the binding behavior of CO and O(2) on Au(13)2012Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 136, nr 2, s. 024312-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present an ab initio density functional theory study of the binding behavior of CO and O(2) molecules to two-and three-dimensional isomers of Au(13) in order to investigate the potential catalytic activity of this cluster towards low-temperature CO oxidation. First, we scanned the potential energy surface of Au(13) and studied the effect of spin-orbit coupling on the relative stabilities of the 21 isomers we identified. While spin-orbit coupling increases the stability of the three-dimensional more than the two-dimensional isomers, the ground state structure at 0 K remains planar. Second, we systematically studied the binding of CO and O(2) molecules onto the planar and three-dimensional structures lowest in energy. We find that the isomer dimensionality has little effect on the binding of CO to Au(13). O(2), on the other hand, binds significantly to the three-dimensional isomer only. The simultaneous binding of multiple CO molecules decreases the binding energy per molecule. Still, the CO binding remains stronger than the O(2) binding. We did not find a synergetic effect due to the co-adsorption of both molecular species. On the three-dimensional isomer, we find O(2) dissociation to be exothermic with an dissociation barrier of 1.44 eV.

  • 8. Amira, S.
    et al.
    Spangberg, D.
    Hermansson, Kersti
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    OD vibrations and hydration structure in an Al3+(aq) solution from a Car-Parrinello molecular-dynamics simulation2006Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 124, nr 10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The optimized geometry, energetics, and vibrational properties of Al(D2O)(n)(3+) clusters, with n=1,2,4, and 6, have been studied using plane waves, different local basis sets, different methodologies [density-functional theory, MP2, CCSD(T)], and different functionals (BLYP, PBE). Moreover, Car-Parrinello molecular-dynamics (MD) simulations using the BLYP functional, plane waves, and the Vanderbilt ultrasoft pseudopotentials have been performed for an aqueous Al3+ solution with 1 ion and 32 D2O molecules in a periodic box at room temperature, studied for 10 ps. The cluster calculations were performed to pinpoint possible shortcomings of the electronic structure description used in the Car-Parinello MD (CPMD) simulation. For the clusters, the hydration structure and interaction energies calculated with the 'BLYP/plane-wave' approach agree well with high-level ab initio methods but the exchange-correlation functional introduces errors in the OD stretching frequencies (both in the absolute values and in the ion-induced shifts). For the aqueous solution, the CPMD simulation yields structural properties in good agreement with experimental data. The CPMD-simulated OD stretching vibrational band for the first-shell water molecules around Al3+ is strongly downshifted by the influence of the ion and is compared with experimental data from the literature. To make such a comparison meaningful, the influences of a number of systematic effects have been addressed, such as the exchange-correlation functional, the fictitious electron mass, anharmonicity effects, and the small box size in the simulation. Each of these factors (except the last one) is found to affect the OD frequency by 100 cm(-1) or more. The final corrected frequencies agree with experiment within similar to 30 cm(-1) for bulk water but are too little downshifted for the first-shell Al3+(aq) water molecules (by similar to 200 cm(-1)).

  • 9. Andersson, E.
    et al.
    Niskanen, Johannes
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Hedin, L.
    Eland, J. H. D.
    Linusson, P.
    Karlsson, L.
    Rubensson, J. -E
    Carravetta, V.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Feifel, R.
    Core-valence double photoionization of the CS2 molecule2010Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 133, nr 9, s. 094305-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Double photoionization spectra of the CS2 molecule have been recorded using the TOF-PEPECO technique in combination with synchrotron radiation at the photon energies h nu=220, 230, 240, 243, and 362.7 eV. The spectra were recorded in the S 2p and C 1s inner-shell ionization regions and reflect dicationic states formed out of one inner-shell vacancy and one vacancy in the valence region. MCSCF calculations were performed to model the energies of the dicationic states. The spectra associated with a S 2p vacancy are well structured and have been interpreted in some detail by comparison to conventional S 2p and valence photoelectron spectra. The lowest inner-shell-valence dicationic state is observed at the vertical double ionization energy 188.45 eV and is associated with a (2p(3/2))(-1)(2 pi(g))(-1) double vacancy. The spectrum connected to the C 1s vacancy shows a distinct line at 310.8 eV, accompanied by additional broad features at higher double ionization energies. This line is associated with a (C 1s)(-1)(2 pi(g))(-1) double vacancy.

  • 10. Andersson, L. Mauritz
    Quantum dynamics using a discretized coherent state representation: An adaptive phase space method2001Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 115, nr 3, s. 1158-1165Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We introduce a discretized coherent state representation (DCSR) for quantum dynamics. Expansion of a wave function in the nonorthogonal slightly overcomplete set is made with an identity operator computed using an iterative refinement method. Calculating the inverse of the overlap matrix is not necessary. The result is an accurate and efficient representation, where you only put basis functions in the region of phase space where the wave function is nonvanishing. Compared to traditional spatial grid methods, fewer grid points are needed. The DCSR can be viewed as an application of the Weyl-Heisenberg frame and extends it into a useful computational method. A scheme for fully quantum mechanical propagation is constructed and applied to the realistic problem of highly excited vibration in the heavy diatomic molecule Rb-2. Compared to split-operator propagation in a conventional spatial grid, an order of magnitude longer time steps can be taken and fewer grid points are needed. The computational effort scales linearly with the number of basis functions. Nonreflecting boundary conditions are a natural property of the representation and is illustrated in a model of predissociation.

  • 11.
    Anghel, Clara
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Dong, Qian
    Isotopic investigation of the transport of oxygen species in Y-stabilized zirconiaIngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690Artikel i tidskrift (Övrigt vetenskapligt)
  • 12.
    Aquilante, Francesco
    et al.
    Ecole Polytech Fed Lausanne EPFL, Theory & Simulat Mat THEOS, CH-1015 Lausanne, Switzerland.;Ecole Polytech Fed Lausanne EPFL, Natl Ctr Computat Design & Discovery Novel Mat MA, CH-1015 Lausanne, Switzerland..
    Autschbach, Jochen
    SUNY Buffalo, Dept Chem, Buffalo, NY 14260 USA..
    Baiardi, Alberto
    Swiss Fed Inst Technol, Phys Chem Lab, Vladimir Prelog Weg 2, CH-8093 Zurich, Switzerland..
    Battaglia, Stefano
    Uppsala universitet, Organisk kemi.
    Borin, Veniamin A.
    Hebrew Univ Jerusalem, Inst Chem, Fritz Haber Ctr Mol Dynam Res, IL-9190401 Jerusalem, Israel..
    Chibotaru, Liviu F.
    Katholieke Univ Leuven, Dept Chem, Celestijnenlaan 200F, B-3001 Leuven, Belgium..
    Conti, Irene
    Univ Bologna, Dipartimento Chim Ind Toso Montanari, Viale Risorgimento 4, I-40136 Bologna, Italy..
    De Vico, Luca
    Univ Siena, Dipartimento Biotecnol Chim & Farm, Via Aldo Moro 2, I-53100 Siena, Italy..
    Delcey, Mickael G
    Uppsala universitet, Teoretisk kemi.
    Fernández Galván, Ignacio
    Uppsala universitet, Organisk kemi.
    Ferre, Nicolas
    Aix Marseille Univ, CNRS, Inst Chim Radicalaire, Marseille, France..
    Freitag, Leon
    Swiss Fed Inst Technol, Phys Chem Lab, Vladimir Prelog Weg 2, CH-8093 Zurich, Switzerland..
    Garavelli, Marco
    Univ Bologna, Dipartimento Chim Ind Toso Montanari, Viale Risorgimento 4, I-40136 Bologna, Italy..
    Gong, Xuejun
    Natl Univ Singapore, Dept Chem, 3 Sci Dr 3, Singapore 117543, Singapore..
    Knecht, Stefan
    Swiss Fed Inst Technol, Phys Chem Lab, Vladimir Prelog Weg 2, CH-8093 Zurich, Switzerland..
    Larsson, Ernst D.
    Lund Univ, Div Theoret Chem, POB 124, S-22100 Lund, Sweden..
    Lindh, Roland
    Uppsala universitet, Organisk kemi.
    Lundberg, Marcus
    Uppsala universitet, Teoretisk kemi.
    Malmqvist, Per Åke
    Lund Univ, Div Theoret Chem, POB 124, S-22100 Lund, Sweden..
    Nenov, Artur
    Univ Bologna, Dipartimento Chim Ind Toso Montanari, Viale Risorgimento 4, I-40136 Bologna, Italy..
    Norell, Jesper
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Odelius, Michael
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Olivucci, Massimo
    Univ Siena, Dipartimento Biotecnol Chim & Farm, Via Aldo Moro 2, I-53100 Siena, Italy.;Bowling Green State Univ, Dept Chem, Bowling Green, OH 43403 USA..
    Pedersen, Thomas B.
    Univ Oslo, Dept Chem, Hylleraas Ctr Quantum Mol Sci, POB 1033 Blindern, N-0315 Oslo, Norway..
    Pedraza-Gonzalez, Laura
    Univ Siena, Dipartimento Biotecnol Chim & Farm, Via Aldo Moro 2, I-53100 Siena, Italy..
    Phung, Quan M.
    Nagoya Univ, Inst Transformat Biomol WPI ITbM, Chikusa Ku, Nagoya, Aichi 4648602, Japan..
    Pierloot, Kristine
    Katholieke Univ Leuven, Dept Chem, Celestijnenlaan 200F, B-3001 Leuven, Belgium..
    Reiher, Markus
    Swiss Fed Inst Technol, Phys Chem Lab, Vladimir Prelog Weg 2, CH-8093 Zurich, Switzerland..
    Schapiro, Igor
    Hebrew Univ Jerusalem, Inst Chem, Fritz Haber Ctr Mol Dynam Res, IL-9190401 Jerusalem, Israel..
    Segarra-Marti, Javier
    Imperial Coll London, Dept Chem, Mol Sci Res Hub, White City Campus,80 Wood Lane, London W12 0BZ, England..
    Segatta, Francesco
    Univ Bologna, Dipartimento Chim Ind Toso Montanari, Viale Risorgimento 4, I-40136 Bologna, Italy..
    Seijo, Luis
    Univ Autonoma Madrid, Dept Quim, Inst Univ Ciencia Mat Nicolas Cabrera, Madrid 28049, Spain.;Univ Autonoma Madrid, Condensed Matter Phys Ctr IFIMAC, Madrid 28049, Spain..
    Sen, Saumik
    Hebrew Univ Jerusalem, Inst Chem, Fritz Haber Ctr Mol Dynam Res, IL-9190401 Jerusalem, Israel..
    Sergentu, Dumitru-Claudiu
    SUNY Buffalo, Dept Chem, Buffalo, NY 14260 USA..
    Stein, Christopher J.
    Swiss Fed Inst Technol, Phys Chem Lab, Vladimir Prelog Weg 2, CH-8093 Zurich, Switzerland..
    Ungur, Liviu
    Natl Univ Singapore, Dept Chem, 3 Sci Dr 3, Singapore 117543, Singapore..
    Vacher, Morgane
    Univ Nantes, Lab CEISAM UMR CNRS 6230, F-44300 Nantes, France..
    Valentini, Alessio
    Univ Liege, Res Unit MolSys, Theoret Phys Chem, Allee 6 Aout 11, B-4000 Liege, Belgium..
    Veryazov, Valera
    Lund Univ, Div Theoret Chem, POB 124, S-22100 Lund, Sweden..
    Modern quantum chemistry with [Open]Molcas2020Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 152, nr 21Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    MOLCAS/OpenMolcas is an ab initio electronic structure program providing a large set of computational methods from Hartree-Fock and density functional theory to various implementations of multiconfigurational theory. This article provides a comprehensive overview of the main features of the code, specifically reviewing the use of the code in previously reported chemical applications as well as more recent applications including the calculation of magnetic properties from optimized density matrix renormalization group wave functions.

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  • 13. Baev, A.
    et al.
    Gel'mukhanov, Faris
    KTH, Tidigare Institutioner (före 2005), Bioteknologi.
    Macak, P.
    Luo, Yi
    KTH, Tidigare Institutioner (före 2005), Bioteknologi.
    Ågren, Hans
    KTH, Tidigare Institutioner (före 2005), Bioteknologi.
    General theory for pulse propagation in two-photon active media2002Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 117, nr 13, s. 6214-6220Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The propagation of laser pulses of different lengths in nonlinear media of organic absorbers is described starting out from a recently suggested dynamical theory for two-photon absorption (TPA) of molecules in solutions [J. Opt. Soc. Am. B 19, 937 (2002)]. The roles of saturation effects and pulse duration on the suppression of TPA are emphasized. The numerical simulations of the pulse propagation are performed for a two-photon active charge transfer molecule using molecular parameters obtained from first principle calculations.

  • 14. Baraldi, Alessandro
    et al.
    Vesselli, Erik
    Bianchettin, Laura
    Comelli, Giovanni
    Lizzit, Silvano
    Petaccia, Luca
    de Gironcoli, Stefano
    Locatelli, Andrea
    Mentes, T. Onur
    Aballe, Lucia
    Weissenrieder, Jonas
    Lund University.
    Andersen, Jesper N.
    The (1x1)-> hexagonal structural transition on Pt(100) studied by high-energy resolution core level photoemission2007Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 127, nr 16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The (1 x 1)-> quasihexagonal (HEX) phase transition on a clean Pt(100) surface was investigated by monitoring the time evolution of the Pt4f(7/2) core level photoemission spectra. The spectral component originating from the atoms forming the (1 x .1) metastable unreconstructed surface was found at -570 +/- 20 meV with respect to the bulk peak. Ab initio calculations based on density functional theory confirmed the experimental assignment. At temperatures above 370 K, the (1 x 1) phase irreversibly reverts to the more stable HEX phase, characterized by a surface core level shifted component at -185 +/- 40 meV. By analyzing the intensity evolution of the core level components, measured at different temperatures in the range of 393-475 K, we determined the activation energy of the phase transformation, E=0.76 +/- 0.04 eV. This value is considerably lower than the one previously determined by means of low energy electron diffraction. Possible reasons for this discrepancy are discussed.

  • 15. Bast, R.
    et al.
    Saue, T.
    Henriksson, J.
    Norman, P.
    Role of noncollinear magnetization for the first-order electric-dipole hyperpolarizability at the four-component Kohn-Sham density functional theory level2009Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 130, nr 2, artikel-id 024109Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The quadratic response function has been derived and implemented at the adiabatic four-component Kohn-Sham density functional theory level with inclusion of noncollinear spin magnetization and gradient corrections in the exchange-correlation functional-a work that is an extension of our previous report where magnetization dependencies in the exchange-correlation functional were ignored [J. Henriksson, T. Saue, and P. Norman, J. Chem. Phys. 128, 024105 (2008)]. The electric-field induced second-harmonic generation experiments on CF3 Cl and CF3 Br are addressed by a determination of Β- (-2ω;ω,ω) for a wavelength of 694.3 nm, and the same property is also determined for CF3 I. The relativistic effects on the static hyperpolarizability for the series of molecules amount to 1%, 5%, and 9%, respectively. At the experimental wavelength, the contributions to Β due to the magnetization dependence in the exchange-correlation functional are negligible for CF3 Cl and CF3 Br and small for CF 3 I. The noticeable effect of magnetization in the latter case is attributed to a near two-photon resonance with the excited state 1 E3 (nonrelativistic notation). It is emphasized, however, that the effect of magnetization on Β for CF3 I is negligible both in comparison to the total relativistic correction as well as to the effects of electron correlation. It is concluded that, in calculations of hyperpolarizabilities under nonresonant conditions, the magnetization dependence in the exchange-correlation functional may be ignored. © 2009 American Institute of Physics.

  • 16. Behringer, H.
    et al.
    Eichhorn, Ralf
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Brownian dynamics simulations with hard-body interactions: Spherical particles2012Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, nr 16, s. 164108-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel approach to account for hard-body interactions in (overdamped) Brownian dynamics simulations is proposed for systems with non-vanishing force fields. The scheme exploits the analytically known transition probability for a Brownian particle on a one-dimensional half-line. The motion of a Brownian particle is decomposed into a component that is affected by hard-body interactions and into components that are unaffected. The hard-body interactions are incorporated by replacing the affected component of motion by the evolution on a half-line. It is discussed under which circumstances this approach is justified. In particular, the algorithm is developed and formulated for systems with space-fixed obstacles and for systems comprising spherical particles. The validity and justification of the algorithm is investigated numerically by looking at exemplary model systems of soft matter, namely at colloids in flow fields and at protein interactions. Furthermore, a thorough discussion of properties of other heuristic algorithms is carried out.

  • 17.
    Belonoshko, Anatoly B.
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    LeBacq, O.
    Ahuja, Rajeev
    Johansson, Börje
    KTH, Tidigare Institutioner (före 2005), Materialvetenskap.
    Molecular dynamics study of phase transitions in Xe2002Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 117, nr 15, s. 7233-7244Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A full account is given of our recent theoretical discovery [A. B. Belonoshko, R. Ahuja, and B. Johansson, Phys. Rev. Lett. 87, 165505 (2001)] of the fcc-bcc transition in Xe at high pressure and temperature. The interaction model and method for calculating phase boundaries are exhaustively tested by independent methods. The model was carefully checked against experimental data and results of ab initio molecular dynamics and it was found to perform very well. The two-phase method employed for finding the melting transition was compared with the robust thermodynamic approach and was found to provide data in exact agreement with the latter. The deviation of the calculated melting curve from the experimental one is quite tolerable at low pressures. After a reinterpretation of the experimental data, our results are also in good agreement with recent diamond anvil cell experiments. At a pressure of around 25 GPa and a temperature of about 2700 K, we find a triple fcc-bcc-liquid point. The fcc-bcc boundary is calculated without reference to the experimental data, in contrast to our previous work, and found to be in nice agreement with previous calculations as well as with the experimental data points, which, however, were interpreted as melting. Our finding concerning the fcc-bcc transition is confirmed by the direct molecular dynamics simulation of the fcc, bcc, and liquid phases in the same computational cell. In this simulation, it was observed that while the fcc phase melts, the bcc structure solidifies. Since Xe is a typical rare-gas solid, the fcc-bcc transition can now be expected for a number of other van der Waals systems, first of all in Ar and Kr. Our finding suggests, that the transition from close packed to bcc structure might be more common at high pressure and high temperature than was previously anticipated. The performed thorough test of methods and models in this study leads us to suggest that the original interpretation of experimental results is erroneous.

  • 18.
    Belonoshko, Anatoly B.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Kondenserade materiens teori.
    Rosengren, Anders
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Kondenserade materiens teori.
    Skorodumova, N. V.
    Bastea, S.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Shock wave propagation in dissociating low-Z liquids: D-22005Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 122, nr 12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present direct molecular dynamics simulations of shock wave propagation in liquid deuterium for a wide range of impact velocities. The calculated Hugoniot is in perfect agreement with the gas-gun data as well as with the most recent experimental data. At high impact velocities we observe a smearing of the shock wave front and propagation of fast dissociated molecules well ahead of the compressed region. This smearing occurs due to the fast deuterium dissociation at the shock wave front. The experimental results are discussed in view of this effect.

  • 19.
    Bergström, Lars Magnus
    KTH, Tidigare Institutioner (före 2005), Kemi.
    Derivation of expressions for the spontaneous curvature, mean and Gaussian bending constants of thermodynamically open surfactant monolayers and bilayers2003Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 118, nr 3, s. 1440-1452Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have derived expressions for the spontaneous curvature H-0, the mean and Gaussian bending constants, k(c) and (k) over bar (c), respectively, for a surfactant film of finite thickness that is open in a thermodynamic sense. Geometrical packing constraints are taken into account and give rise to explicit large and important contributions to k(c), (k) over bar (c), and k(c)H(0). From its contribution to the latter quantity we may deduce that surfactant aggregates (micelles, vesicles, microemulsion droplets) are expected to dramatically increase their size with increasing surfactant tail length. Moreover, the coupling between free energy contributions related to surfactant head group and tail with geometrical packing constraints give rise to dominant terms on the form 2xi(p)H(0), where xi(p) is the thickness of a planar film, in the expressions for k(c). In the case of repulsive head group effects that favor a large spontaneous curvature, such as electrostatics, these terms raise k(c) and thus increase the rigidity of the film. Due to the constraint of constant free monomer chemical potentials, the composition of the film becomes a function of curvature. As a result, the ability of a surfactant film to have different surfactant compositions in differently curved parts (e.g., inner and outer layer of a vesicle, central parts and end caps of rod or threadlike micelles, etc.) may considerably reduce k(c), whereas (k) over bar

  • 20.
    Bergström, Lars Magnus
    KTH, Tidigare Institutioner (före 2005), Kemi.
    Thermodynamics of anisotropic surfactant micelles. I. The influence of curvature free energy on the micellar size and shape2000Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 113, nr 13, s. 5559-5568Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel theory for the structural behavior of surfactant micelles is expounded. The micelles are considered to be generally shaped as triaxial tablets with distinct thickness width and length, respectively, and may become spherical, spherocylindrical or disk-shaped in the special cases where two or more of the dimensions are equal. It is demonstrated that the average width and length of a tablet-shaped micelle with a fixed thickness is mainly determined by two constants, k(1) and k(2), related to the first and second order correction in curvature of the micellar end caps. The size of the micelles is found to be mainly determined by k(1), whereas k(2) influences the shape, i.e., the length-to-width ratio, of the micelles so that the micellar size increases with increasing k(1) and the length-to-width ratio decreases with increasing k(2). Hence, large positive values of k(2) promote the formation of tablets rather than very long spherocylinders. An additional parameter related to the curvature of the straight cylindrical rims may influence the structure of the tablet-shaped micelles insofar k(2) is close to or below zero.

  • 21.
    Bergström, Lars Magnus
    KTH, Tidigare Institutioner (före 2005), Kemi.
    Thermodynamics of anisotropic surfactant micelles. II. A molecular interpretation of the micellar curvature free energy2000Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 113, nr 13, s. 5569-+Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Explicit expressions have been derived for the two curvature constants k(1) and k(2) that mainly influence the size and shape, respectively, of generally shaped micelles (triaxial tablets with a thickness < width < length). It is found that geometrical packing constraints, together with an unfavorable hydrocarbon/water interfacial tension gamma(hc/w), give rise to a large and positive contribution to both k(1) and k(2) that increases with the micellar thickness (equivalent to surfactant tail length) as well as with gamma(hc/w). The constant k(1) that mainly influence the size of the micelles may be brought down by electrostatics to values where rather small micelles are able to form. However, electrostatics also have a tendency to increase the constant k(2) that mainly affects the length-to-width ratio of the micelles so that the smaller micelles are predicted to be rather disklike, i.e., with a low length-to-width ratio. In addition, residual head group effects as well as the free energy contribution due to the hydrocarbon chains may influence the micellar size and shape. In particular, it is demonstrated that mixing of two surfactants reduces k(2) and promotes the formation of elongated micelles with a large length-to-width ratio whereas k(1), and thus the overall size of the micelles, is only slightly influenced. The effect of mixing is predicted to increase with increasing asymmetry between the surfactants mixed in the micelles with respect to head group size and charge number as well as hydrophobic tail volume.

  • 22.
    Besharat, Zahra
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Materialfysik, MF. KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Halldin Stenlid, Joakim
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Soldemo, Markus
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Materialfysik, MF.
    Marks, Kess
    Önsten, Anneli
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Materialfysik, MF.
    Johnson, Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Öström, Henrik
    Weissenrieder, Jonas
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Brinck, Tore
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Göthelid, Mats
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Materialfysik, MF.
    Dehydrogenation of methanol on Cu2O(100) and (111)2017Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, nr 24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adsorption and desorption of methanol on the (111) and (100) surfaces of  Cu2O have been studied using high-resolution photoelectron spectroscopy in the temperature range 120–620 K, in combination with density functional theorycalculations and sum frequency generation spectroscopy. The bare (100) surfaceexhibits a (3,0; 1,1) reconstruction but restructures during the adsorption process into a Cu-dimer geometry stabilized by methoxy and hydrogen binding in Cu-bridge sites. During the restructuring process, oxygen atoms from the bulk that can host hydrogen appear on the surface. Heating transforms methoxy to formaldehyde, but further dehydrogenation is limited by the stability of the surface and the limited access to surface oxygen. The (√3 × √3)R30°-reconstructed (111) surface is based on ordered surface oxygen and copper ions and vacancies, which offers a palette of adsorption and reaction sites. Already at 140 K, a mixed layer of methoxy, formaldehyde, and CHxOy is formed. Heating to room temperature leaves OCH and CHx. Thus both CH-bond breaking and CO-scission are active on this  surface at low temperature. The higher ability to dehydrogenate methanol on (111) compared to (100) is explained by the multitude of adsorption sites and, in particular, the availability of surfaceoxygen.

  • 23. Bidermane, I.
    et al.
    Luder, J.
    Boudet, S.
    Zhang, T.
    Ahmadi, Sareh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Grazioli, C.
    Bouvet, M.
    Rusz, J.
    Sanyal, B.
    Eriksson, O.
    Brena, B.
    Puglia, C.
    Witkowski, N.
    Experimental and theoretical study of electronic structure of lutetium bi-phthalocyanine2013Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, nr 23, s. 234701-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using Near Edge X-Ray Absorption Fine Structure (NEXAFS) Spectroscopy, the thickness dependent formation of Lutetium Phthalocyanine (LuPc2) films on a stepped passivated Si(100)2x1 reconstructed surface was studied. Density functional theory (DFT) calculations were employed to gain detailed insights into the electronic structure. Photoelectron spectroscopy measurements have not revealed any noticeable interaction of LuPc2 with the H-passivated Si surface. The presented study can be considered to give a comprehensive description of the LuPc2 molecular electronic structure. The DFT calculations reveal the interaction of the two molecular rings with each other and with the metallic center forming new kinds of orbitals in between the phthalocyanine rings, which allows to better understand the experimentally obtained NEXAFS results.

  • 24. Bishop, D. M.
    et al.
    Norman, P.
    Effects of vibration on the polarizability and the first and second hyperpolarizabilities of HF, HCl, and HBr1999Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 111, nr 7, s. 3042-3050Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report calculations, using electron uncorrelated and correlated wave functions, of the electronic and vibrational properties which pertain to certain nonlinear optical properties for HF, HCl, and HBr. Our main focus is on vibrational effects (zero-point-vibrational averaging and pure vibration). Analysis of the results obtained at various levels of approximation indicates that first-order perturbation theory is generally adequate for finding the zero-point-vibrational-averaging corrections for these molecules and that complete second-order perturbation theory nearly always gives reliable results for the pure vibrational corrections. Attention is drawn to some differences with previously published results for these properties. © 1999 American Institute of Physics.

  • 25. Bittererova, M.
    et al.
    Ostmark, H.
    Brinck, Tore
    KTH, Tidigare Institutioner (före 2005), Kemi.
    A theoretical study of the azide (N-3) doublet states. A new route to tetraazatetrahedrane (N-4): N+N-3 -> N-42002Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 116, nr 22, s. 9740-9748Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The potential energy surfaces for the low-lying doublet states of the azide radical (N-3) have been computed at the complete active space self-consistent field (CASSCF) level with the CAS(15,12) active space. The cc-pVTZ and aug-cc-pVTZ basis sets have been employed throughout the present work. Energies, geometries and harmonic frequencies were determined for the N-3 linear ground electronic state ((2)Pi(g)), a stable C-2v ring structure (B-2(1)), and a C-s transition state ((2)A(')) connecting the ring and linear structures. Other N-3 (C-2v) stationary points ((2)A(2), B-2(1), and (2)A(1)) have been characterized, as well. The vertical excitation energies for the doublet excited states of the N-3 linear ((2)Pi(g)) and stable ring (B-2(1)) isomers were calculated using CASSCF and multireference configuration interaction [MRCI-SD(Q)] methods. A new route to tetraazatetrahedrane [N-4(T-d)] has been proposed on the N-4 singlet potential energy surface within C-s symmetry. MRCI-SD(Q) calculations predict that N-4 (T-d) can be formed from atomic nitrogen in the D-2 state and N-3 (C-2v, B-2(1)) in a barrierless exothermic reaction. The energy difference (D-0) is 135.4 kcal/mol at the MRCI-SD(Q) level.

  • 26. Bohner, B.
    et al.
    Endrodi, Balazs
    Horváth, D.
    Tóth, Á.
    Flow-driven pattern formation in the calcium-oxalate system2016Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 144Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The precipitation reaction of calcium oxalate is studied experimentally in the presence of spatial gradients by controlled flow of calcium into oxalate solution. The density difference between the reactants leads to strong convection in the form of a gravity current that drives the spatiotemporal pattern formation. The phase diagram of the system is constructed, the evolving precipitate patterns are analyzed and quantitatively characterized by their diameters and the average height of the gravity flow. The compact structures of calcium oxalate monohydrate produced at low flow rates are replaced by the thermodynamically unstable calcium oxalate dihydrate favored in the presence of a strong gravity current.

  • 27.
    Brand, Manuel
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. KTH Royal Inst Technol, Dept Theoret Chem & Biol, Sch Engn Sci Chem Biotechnol & Hlth, SE-10691 Stockholm, Sweden..
    Ahmadzadeh, Karan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. KTH Royal Inst Technol, Dept Theoret Chem & Biol, Sch Engn Sci Chem Biotechnol & Hlth, SE-10691 Stockholm, Sweden..
    Li, Xin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Parallelldatorcentrum, PDC. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. KTH Royal Inst Technol, Dept Theoret Chem & Biol, Sch Engn Sci Chem Biotechnol & Hlth, SE-10691 Stockholm, Sweden..
    Rinkevicius, Zilvinas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Department of Physics, Faculty of Mathematics and Natural Sciences, Kaunas University of Technology, LT-51368 Kaunas, Lithuania.
    Saidi, Wissam A.
    Univ Pittsburgh, Dept Mech Engn & Mat Sci, Pittsburgh, PA 15261 USA..
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. KTH Royal Inst Technol, Dept Theoret Chem & Biol, Sch Engn Sci Chem Biotechnol & Hlth, SE-10691 Stockholm, Sweden..
    Size-dependent polarizabilities and van der Waals dispersion coefficients of fullerenes from large-scale complex polarization propagator calculations2021Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 154, nr 7, artikel-id 074304Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    While the anomalous non-additive size-dependencies of static dipole polarizabilities and van der Waals C-6 dispersion coefficients of carbon fullerenes are well established, the widespread reported scalings for the latter (ranging from N-2.2 to N-2.8) call for a comprehensive first-principles investigation. With a highly efficient implementation of the linear complex polarization propagator, we have performed Hartree-Fock and Kohn-Sham density functional theory calculations of the frequency-dependent polarizabilities for fullerenes consisting of up to 540 carbon atoms. Our results for the static polarizabilities and C-6 coefficients show scalings of N-1.2 and N-2.2, respectively, thereby deviating significantly from the previously reported values obtained with the use of semi-classical/empirical methods. Arguably, our reported values are the most accurate to date as they represent the first ab initio or first-principles treatment of fullerenes up to a convincing system size.

  • 28.
    Brandt, Erik G.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk biologisk fysik.
    Edholm, Olle
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk biologisk fysik.
    Stretched exponential dynamics in lipid bilayer simulations2010Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 133, nr 11, s. 115101-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The decay of fluctuations in fluid biomembranes is strongly stretched and nonexponential on nanometer lengthscales. We report on calculations of structural correlation functions for lipid bilayer membranes from atomistic and coarse-grained molecular dynamics simulations. The time scales extend up to microseconds, whereas the linear size of the largest systems is around 50 nm. Thus, we can cover the equilibrium dynamics of wave vectors over two orders of magnitude (0.2-20 nm(-1)). The time correlations observed in the simulations are best described by stretched exponential functions, with exponents of 0.45 for the atomistic and 0.60 for the coarse-grained model. Area number density fluctuations, thickness fluctuations, and undulations behave dynamically in a similar way and have almost exactly the same dynamics for wavelengths below 3 nm, indicating that in this regime undulations and thickness fluctuations are governed by in-plane density fluctuations. The out-of-plane height fluctuations are apparent only at the longest wavelengths accessible in the simulations (above 6 nm). The effective correlation times of the stretched exponentials vary strongly with the wave vector. The variation fits inverse power-laws that change with wavelength. The exponent is 3 for wavelengths smaller than about 1.25 nm and switches to 1 above this. There are indications for a switch to still another exponent, 2, for wavelengths above 20 nm. Compared to neutron spin-echo (NSE) experiments, the simulation data indicate a faster relaxation in the hydrodynamic limit, although an extrapolation of NSE data, as well as inelastic neutron scattering data, is in agreement with our data at larger wave vectors.

  • 29.
    Brena, Barbara
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Carniato, S.
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Functional and basis set dependence of K-edge shake-up spectra of molecules2005Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 122, nr 18, s. 184316-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A straightforward approach for computing the K -edge shake-up spectra of molecules based on equivalent core-hole linear response theory at both Hartree-Fock and density functional theory levels is proposed. Benchmark calculations have been performed to explore its sensitivity to different types of functionals and basis sets for the carbon 1s shake-up spectra of benzene and metal-free phthalocyanine (H2 Pc). A very good agreement with previous theoretical and experimental works for the benzene molecule has been obtained for all the functionals and basis sets tested. Electron correlation is found to be essential for a good description of the H2 Pc system, whose experimental C 1s shake-up spectrum is best reproduced by the hybrid density functional.

  • 30.
    Brena, Barbara
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Characterization of the electronic structure of C50Cl10 by means of soft x-ray spectroscopies2005Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 123, nr 24, s. 244305-1-244305-4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electronic structure of the last synthesized fullerene molecule, the C50Cl10, has been characterized by theoretical simulation of x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and near-edge x-ray-absorption fine structure. All the calculations were performed at the gradient-corrected and hybrid density-functional theory levels. The combination of these techniques provides detailed information about the valence band and the unoccupied molecular orbitals, as well as about the carbon core orbitals.

  • 31.
    Brena, Barbara
    et al.
    KTH, Tidigare Institutioner (före 2005), Bioteknologi.
    Luo, Yi
    KTH, Tidigare Institutioner (före 2005), Bioteknologi.
    Electronic structures of azafullerene C48N122003Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 119, nr 14, s. 7139-7144Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two recently proposed low-energy azafullerene C48N12 isomers have been theoretically characterized using x-ray spectroscopies. The x-ray photoelectron spectroscopy, the near-edge absorption fine structure, the x-ray emission spectroscopy, and the ultraviolet photoelectron spectroscopy for both isomers have been predicted at the gradient-corrected density functional theory level. These spectroscopies together give a comprehensive insight of the electronic structure on the core, valence, and unoccupied orbitals. They have also provided a convincing way for identifying the isomer structures.

  • 32.
    BRINCK, T
    et al.
    University of New Orleans.
    MURRAY, JS
    POLITZER, P
    POLARIZABILITY AND VOLUME1993Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 98, nr 5, s. 4305-4306Artikel i tidskrift (Refereegranskat)
  • 33.
    Brumboiu, Iulia E.
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Pohang Univ Sci & Technol POSTECH, Dept Chem, Pohang 37673, South Korea.
    Rehn, Dirk R.
    Heidelberg Univ, Interdisciplinary Ctr Sci Comp, D-69120 Heidelberg, Germany..
    Dreuw, Andreas
    Heidelberg Univ, Interdisciplinary Ctr Sci Comp, D-69120 Heidelberg, Germany..
    Rhee, Young Min
    Korea Adv Inst Sci & Technol, Dept Chem, Daejeon 34141, South Korea..
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Analytical gradients for core-excited states in the algebraic diagrammatic construction (ADC) framework2021Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 155, nr 4, artikel-id 044106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Expressions for analytical molecular gradients of core-excited states have been derived and implemented for the hierarchy of algebraic diagrammatic construction (ADC) methods up to extended second-order within the core-valence separation (CVS) approximation. We illustrate the use of CVS-ADC gradients by determining relaxed core-excited state potential energy surfaces and optimized geometries for water, formic acid, and benzene. For water, our results show that in the dissociative lowest core-excited state, a linear configuration is preferred. For formic acid, we find that the O K-edge lowest core-excited state is non-planar, a fact that is not captured by the equivalent core approximation where the core-excited atom with its hole is replaced by the "Z + 1" neighboring atom in the periodic table. For benzene, the core-excited state gradients are presented along the Jahn-Teller distorted geometry of the 1s -> pi* excited state. Our development may pave a new path to studying the dynamics of molecules in their core-excited states.

  • 34.
    Brumboiu, Iulia Emilia
    et al.
    Pohang Univ Sci & Technol POSTECH, Dept Chem, Pohang 37673, South Korea.;Nicolaus Copernicus Univ, Fac Phys, Astron & Informat, PL-87100 Torun, Poland..
    Fransson, Thomas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Core-hole delocalization for modeling x-ray spectroscopies: A cautionary tale2022Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 156, nr 21, artikel-id 214109Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of core-hole delocalization for x-ray photoelectron, x-ray absorption, and x-ray emission spectrum calculations is investigated in detail using approaches including response theory, transition-potential methods, and ground state schemes. The question of a localized/delocalized vacancy is relevant for systems with symmetrically equivalent atoms, as well as near-degeneracies that can distribute the core orbitals over several atoms. We show that the issues relating to core-hole delocalization are present for calculations considering explicit core-hole states, e.g., when using a core-excited or core-ionized reference state or for fractional occupation numbers. As electron correlation eventually alleviates the issues, but even when using coupled-cluster single-double and perturbative triple, there is a notable discrepancy between core-ionization energies obtained with localized and delocalized core-holes (0.5 eV for the carbon K-edge). Within density functional theory, the discrepancy correlates with the exchange interaction involving the core orbitals of the same spin symmetry as the delocalized core-hole. The use of a localized core-hole allows for a reasonably good inclusion of relaxation at a lower level of theory, whereas the proper symmetry solution involving a delocalized core-hole requires higher levels of theory to account for the correlation effects involved in orbital relaxation. For linear response methods, we further show that if x-ray absorption spectra are modeled by considering symmetry-unique sets of atoms, care has to be taken such that there are no delocalizations of the core orbitals, which would otherwise introduce shifts in absolute energies and relative features.

  • 35.
    Brumboiu, Iulia Emilia
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Prokopiou, G.
    Kronik, L.
    Brena, B.
    Valence electronic structure of cobalt phthalocyanine from an optimally tuned range-separated hybrid functional2017Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, nr 4, artikel-id 044301Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We analyse the valence electronic structure of cobalt phthalocyanine (CoPc) by means of optimally tuning a range-separated hybrid functional. The tuning is performed by modifying both the amount of short-range exact exchange (α) included in the hybrid functional and the range-separation parameter (γ), with two strategies employed for finding the optimal γ for each α. The influence of these two parameters on the structural, electronic, and magnetic properties of CoPc is thoroughly investigated. The electronic structure is found to be very sensitive to the amount and range in which the exact exchange is included. The electronic structure obtained using the optimal parameters is compared to gas-phase photo-electron data and GW calculations, with the unoccupied states additionally compared with inverse photo-electron spectroscopy measurements. The calculated spectrum with tuned γ, determined for the optimal value of α = 0.1, yields a very good agreement with both experimental results and with GW calculations that well-reproduce the experimental data.

  • 36.
    Brumboiu, Iulia
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Korea Adv Inst Sci & Technol, Dept Chem, Daejeon 34141, South Korea..
    Eriksson, Olle
    Uppsala Univ, Dept Phys & Astron, SE-75120 Uppsala, Sweden..
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Atomic photoionization cross sections beyond the electric dipole approximation2019Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 150, nr 4, artikel-id 044306Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A methodology is developed to compute photoionization cross sections beyond the electric dipole approximation from response theory, using Gaussian type orbitals and plane waves for the initial and final states, respectively. The methodology is applied to compute photoionization cross sections of atoms and ions from the first four rows of the periodic table. Analyzing the error due to the plane wave description of the photoelectron, we find kinetic energy and concomitant photon energy thresholds above which the plane wave approximation becomes applicable. The correction introduced by going beyond the electric dipole approximation increases with photon energy and depends on the spatial extension of the initial state. In general, the corrections are below 10% for most elements, at a photon energy reaching up to 12 keV. 2019 Author(s).

  • 37.
    Busson, B.
    et al.
    Univ Paris Saclay, Univ Paris Sud, CNRS, Lab Chim Phys, Batiment 201 P2, F-91405 Orsay, France..
    Dalstein, Laetitia
    KTH, Skolan för kemivetenskap (CHE), Kemi. Laboratoire de Chimie Physique, CNRS, University of Paris-Sud, Université Paris-Saclay, Bâtiment 201 P2, Orsay, France.
    Nonlinear optical response of a gold surface in the visible range: A study by two-color sum-frequency generation spectroscopy. II. Model for metal nonlinear susceptibility2018Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 149, nr 3, artikel-id 034701Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a modeling of the nonlinear optical response of a metal surface in order to account for recent experimental results from two-color Sum-Frequency Generation (SFG) experiments on gold. The model allows calculating the surface and bulk contributions and explicitly separates free and bound electron terms. Contrary to the other contributions, the perpendicular surface component is strongly model-dependent through the surface electron density profiles. We consider three electron density schemes at the surface, with free and bound electrons overlapping or spilling out of the bulk, for its calculation. The calculated SFG signals from the metal rely only on bulk quantities and do not need an explicit definition of the density profiles. In the particular case of gold, when the free electrons overlap with the bound ones or spill out of the bulk, the free electron response completely dominates through the perpendicular surface terms. When the bound electrons spill out, the situation is more balanced, still in favor of the free electrons, with lower amplitudes and different dispersion line shapes. As for silver, the free electron contributions dominate and the calculated slow amplitude growth from blue to red follows the experimental trends.

  • 38.
    Busson, B.
    et al.
    Univ Paris Saclay, Univ Paris Sud, Lab Chim Phys, CNRS, Batiment 201 P2, F-91405 Orsay, France..
    Dalstein, Laetitia
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi. Univ Paris Saclay, Univ Paris Sud, Lab Chim Phys, CNRS, Batiment 201 P2, F-91405 Orsay, France.;KTH Royal Inst Technol, Dept Chem, Sch Chem Sci & Engn, SE-10044 Stockholm, Sweden.;Acad Sinica, Inst Phys, Taipei 11529, Taiwan..
    Nonlinear optical response of a gold surface in the visible range: A study by two-color sum-frequency generation spectroscopy. III. Simulations of the experimental SFG intensities2018Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 149, nr 15, artikel-id 154701Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We model the amplitude line shape and absolute phase of the infrared-visible sum-frequency signals produced by a thiolated polycrystalline gold surface as a function of the visible wavelength. We follow two hypotheses: in the interband scenario, the resonant features are attributed to interband transitions, whereas in the effective surface state scenario, they stem mostly from the excitation of surface transitions. We find that both scenarios lead to a satisfactory account of the experimental data and that only free electrons may spill out of the gold bulk, as expected. For the interband scenario, the balance between free and bound electron contributions to sum-frequency generation has to be adjusted to fit the data. The surface transitions are shown to take their origin inside gold and we investigate the surface states involved in such transitions, with a comparison to the silver surfaces. We finally provide a work program dedicated to discriminate between the two scenarios. Published by AIP Publishing.

  • 39. Callaghan, P. T.
    et al.
    Furo, Istvan
    KTH, Tidigare Institutioner (före 2005), Kemi.
    Diffusion-diffusion correlation and exchange as a signature for local order and dynamics2004Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 120, nr 8, s. 4032-4038Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate the use of new two-dimensional nuclear magnetic resonance experiments in the examination of local diffusional anisotropy under conditions of global isotropy. The methods, known as diffusion-diffusion correlation spectroscopy and diffusion exchange spectroscopy, employ successive pairs of magnetic field gradient pulses, with signal analysis using two-dimensional inverse Laplace transformation. Diffusional anisotropy is measured for water molecules in a polydomain lamellar phase lyotropic liquid crystal, 40 wt % nonionic surfactant C10E3 (C10H21O(CH2CH2O)(6)H) in H2O.

  • 40. Camisasca, G.
    et al.
    Pathak, H.
    Wikfeldt, Kjartan Thor
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Parallelldatorcentrum, PDC. Department of Physics, AlbaNova University Center, Stockholm University, Stockholm, SE-10609, Sweden.
    Pettersson, L. Gunnar M.
    Radial distribution functions of water: Models vs experiments2019Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 151, nr 4, artikel-id 044502Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the temperature behavior of the first four peaks of the oxygen-oxygen radial distribution function of water, simulated by the TIP4P/2005, MB-pol, TIP5P, and SPC/E models and compare to experimental X-ray diffraction data, including a new measurement which extends down to 235 K [H. Pathak et al., J. Chem. Phys. 150, 224506 (2019)]. We find the overall best agreement using the MB-pol and TIP4P/2005 models. We observe, upon cooling, a minimum in the position of the second shell simulated with TIP4P/2005 and SPC/E potentials, located close to the temperature of maximum density. We also calculated the two-body entropy and the contributions coming from the first, second, and outer shells to this quantity. We show that, even if the main contribution comes from the first shell, the contribution of the second shell can become important at low temperature. While real water appears to be less ordered at short distance than obtained by any of the potentials, the different water potentials show more or less order compared to the experiments depending on the considered length-scale.

  • 41.
    Camisasca, Gaia
    et al.
    Stockholm Univ, Dept Phys, S-10691 Stockholm, Sweden..
    Galamba, Nuno
    Univ Lisbon, Fac Sci, Ctr Chem & Biochem, C8 Campo Grande, P-1749016 Lisbon, Portugal.;Univ Lisbon, Fac Sci, Biosyst & Integrat Sci Inst, C8 Campo Grande, P-1749016 Lisbon, Portugal..
    Wikfeldt, Kjartan Thor
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Parallelldatorcentrum, PDC. Stockholm Univ, Dept Phys, S-10691 Stockholm, Sweden..
    Pettersson, Lars G. M.
    Stockholm Univ, Dept Phys, S-10691 Stockholm, Sweden..
    Translational and rotational dynamics of high and low density TIP4P/2005 water2019Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 150, nr 22, artikel-id 224507Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We use molecular dynamics simulations using TIP4P/2005 to investigate the self- and distinct-van Hove functions for different local environments of water, classified using the local structure index as an order parameter. The orientational dynamics were studied through the calculation of the time-correlation functions of different-order Legendre polynomials in the OH-bond unit vector. We found that the translational and orientational dynamics are slower for molecules in a low-density local environment and correspondingly the mobility is enhanced upon increasing the local density, consistent with some previous works, but opposite to a recent study on the van Hove function. From the analysis of the distinct dynamics, we find that the second and fourth peaks of the radial distribution function, previously identified as low density-like arrangements, show long persistence in time. The analysis of the time-dependent interparticle distance between the central molecule and the first coordination shell shows that particle identity persists longer than distinct van Hove correlations. The motion of two first-nearest-neighbor molecules thus remains coupled even when this correlation function has been completely decayed. With respect to the orientational dynamics, we show that correlation functions of molecules in a low-density environment decay exponentially, while molecules in a local high-density environment exhibit bi-exponential decay, indicating that dynamic heterogeneity of water is associated with the heterogeneity among high-density and between high-density and low-density species. This bi-exponential behavior is associated with the existence of interstitial waters and the collapse of the second coordination sphere in high-density arrangements, but not with H-bond strength.

  • 42. Cao, Jun
    et al.
    Fang, Qiu
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Fang, Wei-Hai
    Photoisomerization mechanism of 4-methylpyridine explored by electronic structure calculations and nonadiabatic dynamics simulations2011Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 134, nr 4, s. 044307-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present paper, different electronic structure methods have been used to determine stationary and intersection structures on the ground (S-0) and (1)pi pi* (S-2) states of 4-methylpyridine, which is followed by adiabatic and nonadiabatic dynamics simulations to explore the mechanistic photoisomerization of 4-methylpyridine. Photoisomerization starts from the S-2((1)pi pi*) state and overcomes a small barrier, leading to formation of the prefulvene isomer in the S-0 state via a S-2/S-0 conical intersection. The ultrafast S-2 -> S-0 nonradiative decay and low quantum yield for the photoisomerization reaction were well reproduced by the combined electronic structure calculation and dynamics simulation. The prefulvene isomer was assigned as a long-lived intermediate and suggested to isomerize to 4-methylpyridine directly in the previous study, which is not supported by the present calculation. The nonadiabatic dynamics simulation and electronic structure calculation reveal that the prefulvene isomer is a short-lived intermediate and isomerizes to benzvalene form very easily. The benzvalene form was predicted as the stable isomer in the present study and is probably the long-lived intermediate observed experimentally. A consecutive light and thermal isomerization cycle via Dewar isomer was determined and this cycle mechanism is different from that reported in the previous study. It should be pointed out that formation of Dewar isomer from the S-2((1)pi pi*) state is not in competition with the isomerization to the prefulvene form. The Dewar structure observed experimentally may originate from other excited states.

  • 43. Carniato, S.
    et al.
    Selles, P.
    Journel, L.
    Guillemin, R.
    Stolte, W. C.
    El Khoury, L.
    Marin, T.
    Gel'mukhanov, Faris
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Lindle, D. W.
    Simon, M.
    Thomson-resonant interference effects in elastic x-ray scattering near the Cl K edge of HCl2012Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, nr 9, s. 094311-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We experimentally observed interference effects in elastic x-ray scattering from gas-phase HCl in the vicinity of the Cl Kedge. Comparison to theory identifies these effects as interference effects between non-resonant elastic Thomson scattering and resonant Raman scattering. The results indicate the non-resonant Thomson and resonant Raman contributions are of comparable strength. The measurements also exhibit strong polarization dependence, allowing an easy identification of the resonant and non-resonant contributions.

  • 44. Carniato, Stéphane
    et al.
    Taïeb, Richard
    Kukk, Edwin
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Brena, Barbara
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    N-K near edge x-ray absorption fine structures of acetonitrile in gas phase2005Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 123, nr 21, s. 214301-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

     The dynamic processes of N(1s) core-hole excitation in gas-phase CH3CN molecule have been studied at both Hartree-Fock and hybrid density-functional theory levels. The vibrational structure is analyzed for fully optimized core-excited states. Frank-Condon factors are obtained using the linear coupling model for various potential surfaces. It is found that the vibrational profile of the N-K absorption can be largely described by a summation of two vibrational progressions: a structure-rich profile of nu((CN)) stretching mode and a large envelope of congestioned vibrational levels related to the strong (-C-CN) terminal bending bond. Excellent agreement between theoretical and experimental spectra is obtained.

  • 45. Carravetta, V.
    et al.
    Ågren, Hans
    KTH, Tidigare Institutioner (före 2005), Bioteknologi.
    Vahtras, Olav
    KTH, Tidigare Institutioner (före 2005), Bioteknologi.
    Jensen, H. J. A.
    Ab initio calculations of molecular resonant photoemission spectra2000Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 113, nr 18, s. 7790-7798Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An ab initio method for calculations of molecular resonant photoemission (RPE) spectra is described. The method includes a multicenter expansion of both the dipole matrix element-direct emission-and the Hamiltonian matrix element between the resonant state and the autoionizing states-resonant emission. These quantities are relevant for the description of the process both in the two-step model, where the spectrum is computed at the resonance energy only, and in the one-step model where, by a K-matrix approach, the direct-to-resonant interference is taken into account and the electronic line profile is fully described. The resonant two-electron matrix elements are evaluated over the core-excited relaxed orbitals with the outgoing Auger electron orbital expanded on an augmented multicentered Gaussian basis set. Stieltjes imaging is shown to work excellently for such Gaussian basis sets giving correct continuum normalization matrix elements even for RPE electron energies as high as 100-1000 eV. A numerical investigation is carried out for the participator decay of the C 1s --> pi* and O 1s --> pi* states of CO.

  • 46. Castleton, C. W. M.
    et al.
    Kullgren, J.
    Hermansson, Kersti
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Tuning LDA+U for electron localization and structure at oxygen vacancies in ceria2007Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 127, nr 24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We examine the real space structure and the electronic structure (particularly Ce4f electron localization) of oxygen vacancies in CeO2 (ceria) as a function of U in density functional theory studies with the rotationally invariant forms of the LDA+U and GGA+U functionals. The four nearest neighbor Ce ions always relax outwards, with those not carrying localized Ce4f charge moving furthest. Several quantification schemes show that the charge starts to become localized at U approximate to 3 eV and that the degree of localization reaches a maximum at similar to 6 eV for LDA+U or at similar to 5.5 eV for GGA+U. For higher U it decreases rapidly as charge is transferred onto second neighbor O ions and beyond. The localization is never into atomic corelike states; at maximum localization about 80-90% of the Ce4f charge is located on the two nearest neighboring Ce ions. However, if we look at the total atomic charge we find that the two ions only make a net gain of (0.2-0.4)e each, so localization is actually very incomplete, with localization of Ce4f electrons coming at the expense of moving other electrons off the Ce ions. We have also revisited some properties of defect-free ceria and find that with LDA+U the crystal structure is actually best described with U=3-4 eV, while the experimental band structure is obtained with U=7-8 eV. (For GGA+U the lattice parameters worsen for U > 0 eV, but the band structure is similar to LDA+U.) The best overall choice is U approximate to 6 eV with LDA+U and approximate to 5.5 eV for GGA+U, since the localization is most important, but a consistent choice for both CeO2 and Ce2O3, with and without vacancies, is hard to find.

  • 47.
    Chen, Xing
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Rinkevicius, Zilvinas
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ruud, K.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Role of zero-point vibrational corrections to carbon hyperfine coupling constants in organic pi radicals2013Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, nr 5, s. 054310-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By analyzing a set of organic pi radicals, we demonstrate that zero-point vibrational corrections give significant contributions to carbon hyperfine coupling constants, in one case even inducing a sign reversal for the coupling constant. We discuss the implications of these findings for the computational analysis of electron paramagnetic spectra based on hyperfine coupling constants evaluated at the equilibrium geometry of radicals. In particular, we note that a dynamical description that involves the nuclear motion is in many cases necessary in order to achieve a semi-quantitatively predictive theory for carbon hyperfine coupling constants. In addition, we discuss the implications of the strong dependence of the carbon hyperfine coupling constants on the zero-point vibrational corrections for the selection of exchange-correlation functionals in density functional theory studies of these constants.

  • 48.
    Chien, Tzu-En
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Processteknologi.
    Hohmann, Lea
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Processteknologi.
    Harding, Dan James
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Processteknologi.
    Near-ambient pressure velocity map imaging2022Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 157, nr 3, artikel-id 034201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a new velocity map imaging instrument for studying molecular beam surface scattering in a near-ambient pressure (NAP-VMI) environment. The instrument offers the possibility to study chemical reaction dynamics and kinetics where higher pressures are either desired or unavoidable, adding a new tool to help close the "pressure gap " between surface science and applied catalysis. NAP-VMI conditions are created by two sets of ion optics that guide ions through an aperture and map their velocities. The aperture separates the high pressure ionization region and maintains the necessary vacuum in the detector region. The performance of the NAP-VMI is demonstrated with results from N2O photodissociation and N-2 scattering from a Pd(110) surface, which are compared under vacuum and at near-ambient pressure (1 x 10(-3) mbar). NAP-VMI has the potential to be applied to, and useful for, a broader range of experiments, including photoelectron spectroscopy and scattering with liquid microjets.

  • 49. Coriani, Sonia
    et al.
    Host, Stinne
    Jansik, Branislav
    Thogersen, Lea
    Olsen, Jeppe
    Jorgensen, Poul
    Reine, Simen
    Pawlowski, Filip
    Helgaker, Trygve
    Salek, Pawel
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Linear-scaling implementation of molecular response theory in self-consistent field electronic-structure theory2007Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 126, nr 15, s. 11930-11935Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A linear-scaling implementation of Hartree-Fock and Kohn-Sham self-consistent field theories for the calculation of frequency-dependent molecular response properties and excitation energies is presented, based on a nonredundant exponential parametrization of the one-electron density matrix in the atomic-orbital basis, avoiding the use of canonical orbitals. The response equations are solved iteratively, by an atomic-orbital subspace method equivalent to that of molecular-orbital theory. Important features of the subspace method are the use of paired trial vectors (to preserve the algebraic structure of the response equations), a nondiagonal preconditioner (for rapid convergence), and the generation of good initial guesses (for robust solution). As a result, the performance of the iterative method is the same as in canonical molecular-orbital theory, with five to ten iterations needed for convergence. As in traditional direct Hartree-Fock and Kohn-Sham theories, the calculations are dominated by the construction of the effective Fock/Kohn-Sham matrix, once in each iteration. Linear complexity is achieved by using sparse-matrix algebra, as illustrated in calculations of excitation energies and frequency-dependent polarizabilities of polyalanine peptides containing up to 1400 atoms.

  • 50.
    Coupette, Fabian
    et al.
    Univ Freiburg, Inst Phys, Hermann Herder Str 3, D-79104 Freiburg, Germany..
    Zhang, Long
    INM Leibniz Inst New Mat, Campus D2 2, D-66123 Saarbrucken, Germany..
    Kuttich, Bjoern
    INM Leibniz Inst New Mat, Campus D2 2, D-66123 Saarbrucken, Germany..
    Chumakov, Andrei
    Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22607 Hamburg, Germany..
    Roth, Stephan V.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22607 Hamburg, Germany.;.
    Gonzalez-Garcia, Lola
    INM Leibniz Inst New Mat, Campus D2 2, D-66123 Saarbrucken, Germany..
    Kraus, Tobias
    INM Leibniz Inst New Mat, Campus D2 2, D-66123 Saarbrucken, Germany.;Saarland Univ, Colloid & Interface Chem, Campus D2 2, D-66123 Saarbrucken, Germany..
    Schilling, Tanja
    Univ Freiburg, Inst Phys, Hermann Herder Str 3, D-79104 Freiburg, Germany..
    Percolation of rigid fractal carbon black aggregates2021Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 155, nr 12, artikel-id 124902Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We examine network formation and percolation of carbon black by means of Monte Carlo simulations and experiments. In the simulation, we model carbon black by rigid aggregates of impenetrable spheres, which we obtain by diffusion-limited aggregation. To determine the input parameters for the simulation, we experimentally characterize the micro-structure and size distribution of carbon black aggregates. We then simulate suspensions of aggregates and determine the percolation threshold as a function of the aggregate size distribution. We observe a quasi-universal relation between the percolation threshold and a weighted average radius of gyration of the aggregate ensemble. Higher order moments of the size distribution do not have an effect on the percolation threshold. We conclude further that the concentration of large carbon black aggregates has a stronger influence on the percolation threshold than the concentration of small aggregates. In the experiment, we disperse the carbon black in a polymer matrix and measure the conductivity of the composite. We successfully test the hypotheses drawn from simulation by comparing composites prepared with the same type of carbon black before and after ball milling, i.e., on changing only the distribution of aggregate sizes in the composites.& nbsp;

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