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  • 1.
    Amft, Martin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Flerskalig materialmodellering.
    Walle, L. E.
    Ragazzon, D.
    Borg, A.
    Uvdal, P.
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Flerskalig materialmodellering.
    Sandell, A.
    A Molecular Mechanism for the Water-Hydroxyl Balance during Wetting of TiO22013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 33, 17078-17083 p.Article in journal (Refereed)
    Abstract [en]

    We show that the formation of the wetting layer and the experimentally observed continuous shift of the H2O-OH balance toward molecular water at increasing coverage on a TiO2(110) surface can be rationalized on a molecular level. The mechanism is based on the initial formation of stable hydroxyl pairs, a repulsive interaction between these pairs, and an attractive interaction with respect to water molecules. The experimental data are obtained by synchrotron radiation photoelectron spectroscopy and interpreted with the aid of density functional theory calculations and Monte Carlo simulations.

  • 2. Arapan, Sergiu
    et al.
    Simak, Sergei I.
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. Uppsala University, Sweden.
    Volume-dependent electron localization in ceria2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 12, 125108Article in journal (Refereed)
    Abstract [en]

    We have performed a numerical study of the process of electron localization in reduced ceria. Our results show that different localized charge distributions can be attained in a bulk system by varying the lattice parameter. We demonstrate that the effect of electron localization is mainly determined by lattice relaxation and an accurate account for the effects of electronic correlation is necessary to achieve localized charge distribution.

  • 3. Barroso da Silva, Fernando Luis
    et al.
    Boström, Mathias
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Effect of Charge Regulation and Ion-Dipole Interactions on the Selectivity of Protein-Nanoparticle Binding2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 14, 4078-4083 p.Article in journal (Refereed)
    Abstract [en]

    We investigate the role of different mesoscopic interactions (Coulomb, charge regulation, and ion-dipole "surface patch" effects) on the binding of bovine serum albumin (BSA) and beta-lactoglobulin (BLG) to a cationic gold nanoparticle (TTMA+). The results demonstrate that the charge-regulation mechanism plays a vital role for selectivity of protein-nanoparticle complexation at low salt concentration. At slightly higher ionic strengths, charge-dipole effects are the dominating driving force. Thus, very small variations in salt concentration strongly influence the origin of complexation.

  • 4. Blanter, M. S.
    et al.
    Dmitriev, V. V.
    Ruban, Andrei V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Ordering in V-O and V-N solid solutions: Computer simulation2014In: Bulletin of the Russian Academy of Sciences: Physics, ISSN 1062-8738, Vol. 78, no 10, 1030-1034 p.Article in journal (Refereed)
    Abstract [en]

    The atomic structures of interstitial solid solutions O and N in V at relatively low concentrations O(N)/V = 1/16 or 1/8 are calculated using the Monte Carlo method. A combined model of long-range interaction between interstitial atoms is employed. The first 12 shells contain ab initio energies and the energies in shells 13–18 are calculated on the basis of a phenomenological model of deformation interaction. The ordered solid solutions are long-period structures with body-centered tetragonal crystal lattices and tetragonality c/a < 1.

  • 5. Bogdanov, V. I.
    et al.
    Popov, V. A.
    Portnoi, V. K.
    Ruban, Andrei V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Method for calculating coefficients of concentrational variations in lattice constants and the distribution of impurity atoms between sublattices in intermetallic compounds2013In: Bulletin of the Russian Academy of Sciences: Physics, ISSN 1062-8738, Vol. 77, no 11, 1360-1362 p.Article in journal (Refereed)
    Abstract [en]

    A method is proposed for calculating coefficients of concentrational variations in lattice constants in solid solutions, based on first-principles determination of the total energy of solid solutions and the continual approximation in the solutions theory, allowing for the deformation interaction of impurity atoms due to distortions of the solvent crystal lattice.

  • 6. Bondarenko, N.
    et al.
    Eriksson, O.
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Hole bipolaron formation at (100) MgO/CaO epitaxial interface2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 12, 125118- p.Article in journal (Refereed)
    Abstract [en]

    Hole localization accompanying the formation of a cation vacancy in bulk MgO and CaO and at the (100) MgO/CaO interface is described using the Heyd-Scuseria-Ernzerhof hybrid functionals and DFT + U method. The ground state is found to be the O-1-O-1 bipolaronic configuration both in bulk oxides and at their interfaces. The ground-state magnetic configuration is a triplet, which has an energy only about 1-2 meV lower than that of the singlet state. The one-centered O-2-O-0 bipolaron was found to be metastable with its stability being enhanced at the interfaces compared to that in bulk oxides. Possible transition between different biplaronic configurations at the interface are analyzed for chosen configurations.

  • 7. Bondarenko, N.
    et al.
    Eriksson, O.
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Polaron mobility in oxygen-deficient and lithium-doped tungsten trioxide2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 16, 165119Article in journal (Refereed)
    Abstract [en]

    Electron localization and polaron mobility in oxygen-deficient as well as Li-doped monoclinic tungsten trioxide have been studied in the adiabatic limit in the framework of density functional theory. We show that small polarons formed in the presence of oxygen vacancy prefer the bipolaronicW(5+)-W5+ configuration, whereas the W6+-W4+ configuration is found to be metastable. Our calculations suggest that bipolarons are tightly bound by the vacancy and therefore largely immobile. On the contrary, polarons formed as a result of Li intercalation can be mobile; the activation energy for polaron jumping in this case varies between 98 and 124 meV depending on the crystallographic direction. The formation of W5+-W5+ bipolarons in Li-WO3 is possible. When situated along [001] the bipolaronic configuration is 8 meV lower in energy than two separate W5+ polarons.

  • 8. Bondarenko, N.
    et al.
    Kvashnin, Y.
    Chico, J.
    Bergman, A.
    Eriksson, O.
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. Uppsala Univ, Sweden.
    Spin-polaron formation and magnetic state diagram in La-doped CaMnO32017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 22, 220401Article in journal (Refereed)
    Abstract [en]

    LaxCa1-xMnO3 (LCMO) has been studied in the framework of density functional theory (DFT) using Hubbard-U correction. We show that the formation of spin polarons of different configurations is possible in the G-type antiferromagnetic phase. We also show that the spin-polaron (SP) solutions are stabilized due to an interplay of magnetic and lattice effects at lower La concentrations and mostly due to the lattice contribution at larger concentrations. Our results indicate that the development of SPs is unfavorable in the C- and A-type antiferromagnetic phases. The theoretically obtained magnetic state diagram is in good agreement with previously reported experimental results.

  • 9. Boström, Mathias
    et al.
    Dou, Maofeng
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Thiyam, Priyadarshini
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Parsons, D. F.
    Malyi, O. I.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Increased porosity turns desorption to adsorption for gas bubbles near water-SiO2 interface2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 7, 075403Article in journal (Refereed)
    Abstract [en]

    We consider theoretically the retarded van der Waals interaction of a small gas bubble in water with a porous SiO2 surface. We predict a possible transition from repulsion to attraction as the surface is made more porous. It highlights that bubbles will interact differently with surface regions with different porosity (i.e., with different optical properties).

  • 10.
    Boström, Mathias
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Huang, Dan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Yang, Weihong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Sernelius, Bo E.
    Lithium atom storage in nanoporous cellulose via surface-induced Li-2 breakage2013In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 104, no 6, 63003- p.Article in journal (Refereed)
    Abstract [en]

    We demonstrate a physical mechanism that enhances a splitting of diatomic Li-2 at cellulose surfaces. The origin of this splitting is a possible surface-induced diatomic-excited-state resonance repulsion. The atomic Li is then free to form either physical or chemical bonds with the cellulose surface and even diffuse into the cellulose layer structure. This allows for an enhanced storage capacity of atomic Li in nanoporous cellulose.

  • 11.
    Boström, Mathias
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Ninham, Barry W.
    Norman, Patrick
    Sernelius, Bo E.
    Resonance interaction induced by metal surfaces catalyzes atom-pair breakage2013In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 87, no 4, 044701- p.Article in journal (Refereed)
    Abstract [en]

    We present the theory for retarded resonance interaction between two identical atoms at arbitrary positions near a metal surface. The dipole-dipole resonance interaction force that binds isotropically excited atom pairs together in free space may turn repulsive close to an ideal (totally reflecting) metal surface. On the other hand, close to an infinitely permeable surface it may turn more attractive. We illustrate numerically how the dipole-dipole resonance interaction between two oxygen atoms near a metal surface may provide a repulsive energy of the same order of magnitude as the ground-state binding energy of an oxygen molecule. As a complement we also present results from density-functional theory.

  • 12.
    Boström, Mathias
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Flerskalig materialmodellering.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Flerskalig materialmodellering.
    Parsons, Drew F.
    Ellingsen, Simen Å.
    Sernelius, Bo E.
    Atmospheric water droplets can catalyse atom pair break-up via surface-induced resonance repulsion2013In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 101, no 4, 43002- p.Article in journal (Refereed)
    Abstract [en]

    We present the theory for a retarded resonance interaction between two identical atoms near a dielectric surface. In free space the resonance interaction between isotropically excited atom pairs is attractive at all atom-atom separations. We illustrate numerically how this interaction between oxygen, sulphur, hydrogen, or nitrogen atom pairs may turn repulsive near water droplets. The results provide evidence of a mechanism causing excited state atom pair breakage to occur in the atmosphere near water droplets.

  • 13.
    Boström, Mathias
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Flerskalig materialmodellering.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Flerskalig materialmodellering.
    Sernelius, Bo E.
    Casimir force between atomically thin gold films2013In: European Physical Journal B: Condensed Matter Physics, ISSN 1434-6028, E-ISSN 1434-6036, Vol. 86, no 2, 43- p.Article in journal (Refereed)
    Abstract [en]

    We have used density functional theory to calculate the anisotropic dielectric functions for ultrathin gold sheets (composed of 1, 3, 6, and 15 atomic layers). Such films are important components in nano-electromechanical systems. When using correct dielectric functions rather than bulk gold dielectric functions we predict an enhanced attractive Casimir-Lifshitz force (at most around 20%) between two atomically thin gold sheets. For thicker sheets the dielectric properties and the corresponding Casimir forces approach those of gold half-spaces. The magnitude of the corrections that we predict should, within the today's level of accuracy in Casimir force measurements, be clearly detectable.

  • 14.
    Cava, Carlos
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. Federal Tecnological University of Paraná.
    Memory Effects on Iron Oxide Filled Carbon Nanotubes2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this Licentiate Thesis, the properties and effects of iron and iron oxide filled carbon nanotube (Fe-CNT) memories are investigated using experimental characterization and quantum physical theoretical models. Memory devices based on the simple assembly of Fe-CNTs between two metallic contacts are presented as a possible application involving the resistive switching phenomena of this material.

    It is known that the electrical conductivity of these nanotubes changes significantly when the materials are exposed to different atmospheric conditions. In this work, the electrical properties of Fe-CNTs and potential applications as a composite material with a semiconducting polymer matrix are investigated. The current voltage characteristics are directly related to the iron oxide that fills the nanotubes, and the effects are strongly dependent on the applied voltage history. Devices made of Fe-CNTs can thereby be designed fo gas sensors and electric memory technologies.

    The electrical characterization of the Fe-CNT devices shows that the devices work with an operation ratio (ON/OFF) of 5 μA. The applied operating voltage sequence is -10 V (to write), +8 V (to read ON), +10 V (to erase) and +8 V (to read OFF) monitoring the electrical current. This operation voltage (reading ON/OFF) must be sufficiently higher than the voltage at which the current peak appears; in most cases the peak position is close to 5 V. The memory effect is based on the switching behavior of the material, and this new feature for technological applications such as resistance random access memory (ReRAM).

    In order to better understand the memory effect in the Fe-CNTs, thesis also presents a study of the surface charge configuration during the operation of the memory devices. Here, Raman scattering analysis is combined with electrical measurements. To identify the material electronic state over a wide range of applied voltage, the Raman spectra are recorded during the device operation and the main Raman active modes of the carbon nanotubes are studied. The applied voltage on the carbon nanotube G-band indicates the presence of Kohn anomalies, which are strongly related to the material’s electronic state. As expected, the same behavior was shown by the other carbon nanotube main modes. The ratio between the D- and G-band intensities (ID/IG) is proposed to be an indicative of the operation’s reproducibility regarding a carbon nanotube memory cell. Moreover, the thermal/electrical characterization indicates the existence of two main hopping charge transports, one between the carbon nanotube walls and the other between the filling and the carbon nanotube. The combination of the hopping processes with the possible iron oxide oxygen migration is suggested as the mechanism for a bipolar resistive switching in this material.

    Based on these studies, it is found that the iron oxide which fills the carbon nanotube, is a major contribution to the memory effect in the material. Therefore, a theoretical study of hematite (i.e., α-Fe2O3) is performed. Here, the antiferromagnetic (AFM) and ferromagnetic (FM) configurations of α-Fe2O3 are analyzed by means of an atomistic first-principles method within the density functional theory. The interaction potential is described by the local spin density approximation (LSDA) with an on-site Coulomb correction of the Fe d-orbitals according to the LSDA+U method. Several calculations on hematite compounds with high and low concentrations of native defects such as oxygen vacancies, oxygen interstitials, and hydrogen interstitials are studied. The crystalline structure, the atomic-resolved density-of-states (DOS), as well as the magnetic properties of these structures are determined.

    The theoretical results are compared to earlier published LSDA studies and show that the Coulomb correction within the LSDA+U method improves both the calculated energy gaps and the local magnetic moment. Compared to the regular LSDA calculations, the LSDA+U method yields a slightly smaller unit-cell volume and a 25% increase of the local magnetic for the most stable AFM phase. This is important to consider when investigating the native defects in the compound. The effect is explained by better localization of the energetically lower Fe d-states in the LSDA+U calculations. Interestingly, due to the localization of the d-states the intrinsic α-Fe2O3 is demonstrated to become an AFM insulator when the LSDA+U method is considered.

    Using the LSDA+U approach, native defects are analyzed. The oxygen vacancies are observed to have a local effect on the DOS due to the electron doping. The oxygen and hydrogen interstitials influence the band-gap energies of the AFM structures. Significant changes are observed in the ground-state energy and also in the magnetization around the defects; this is correlated to Hund’s rules. The presence of the native defects (i.e., vacancies, interstitial oxygen and interstitial hydrogen) in the α-Fe2O3 structures changes the Fe–O and Fe–Fe bonds close to the defects, implying a reduction of the energy gap as well as the local magnetization. The interstitial oxygen strongly stabilizes the AFM phase, also decreases the band-gap energy without forming any defect states in the band-gap region.

  • 15.
    Cava, Carlos Eduardo
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Zarbin, Aldo J.G.
    Roman, Lucimara Stolz
    Resistive switching in iron-oxide-filled carbon nanotubes2014In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 6, no 1, 378-384 p.Article in journal (Refereed)
    Abstract [en]

    Iron-oxide-filled carbon nanotubes have an intriguing charge bipolarization behaviour which allows the material to be applied in resistive memory devices. Raman analysis conducted with an electric field applied in situ shows the Kohn anomalies and a strong modification of the electronic properties related with the applied voltage intensity. As well as, the ID/IG ratio indicated the reversibility of this process. The electric characterization indicated an electronic transport governed by two main kind of charge hopping, one between the filling and nanotube and other between the nanotube shells.

  • 16.
    Cava, Carlos Eduardo
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Roman, Lucimara Stolz
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Effects of native defects on the structural and magnetic properties of hematite alpha-Fe2O32013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 88, no 4, 045136- p.Article in journal (Refereed)
    Abstract [en]

    Antiferromagnetic and ferromagnetic configurations of hematite alpha-Fe2O3 structures have been investigated by first-principles methods, which have been used to theoretically analyze the local structural and magnetic effects due to the presence of interstitial atoms such as hydrogen and oxygen. This study is based on the projector-augmented wave method within the local spin density approximation (LSDA) in addition to an on-site Coulomb correction of the Fe d orbitals (i.e., the LSDA + U-SIC method). The results demonstrate that this correction potential is important in achieving an accurate description of both the structural and the magnetic properties of alpha-Fe2O3. The ground state of alpha-Fe2O3 is the antiferromagnetic phase. The presence of oxygen vacancies, interstitial oxygen, and an interstitial hydrogen decreases the local Fe magnetic moment vertical bar M-s(Fe)vertical bar in both the ferro- and antiferromagnetic phases, although the hydrogen has a rather modest effect. The density of states calculations demonstrate that the presence of interstitial atoms and defects yields a small reduction in the material's electronic gap.

  • 17.
    Chen, Rongzhen
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Band structure and optical properties of CuInSe22014Conference paper (Refereed)
    Abstract [en]

    In this work, the electronic structure and dielectric function of chalcopyrite CuInSe2 are presented. The results are based on the full-potential linearized augmented plane wave (FPLAPW) method using the generalized gradient approximation (GGA) plus an onsite Coulomb interaction U of the Cu d states. The dielectric constant, absorption coefficient and refractive index are explored by means of optical response. The spin-orbit coupling effect is considered for the calculations of electronic structure and optical properties. We find that the results based on our calculation method have good agreement compared with experimental and other earlier simulations results.

  • 18. Chen, Xiaobin
    et al.
    Tian, Fuyang
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Duan, Wenhui
    Chen, Nan-xian
    Interlayer interactions in graphites2013In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, 3046- p.Article in journal (Refereed)
    Abstract [en]

    Based on ab initio calculations of both the ABC- and AB-stacked graphites, interlayer potentials (i.e., graphene-graphene interaction) are obtained as a function of the interlayer spacing using a modified Mobius inversion method, and are used to calculate basic physical properties of graphite. Excellent consistency is observed between the calculated and experimental phonon dispersions of AB-stacked graphite, showing the validity of the interlayer potentials. More importantly, layer-related properties for nonideal structures (e.g., the exfoliation energy, cleave energy, stacking fault energy, surface energy, etc.) can be easily predicted from the interlayer potentials, which promise to be extremely efficient and helpful in studying van der Waals structures.

  • 19. Delczeg-Czirjak, E. K.
    et al.
    Edström, A.
    Werwinski, M.
    Rusz, J.
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Eriksson, O.
    Stabilization of the tetragonal distortion of Fe chi Co1-chi alloys by C impurities: A potential new permanent magnet2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 14, 144403- p.Article in journal (Refereed)
    Abstract [en]

    We have analyzed by density functional theory calculations the structural and magnetic properties of Fe-Co alloys doped by carbon. In analogy with the formation of martensite in steels we predict that such a structure also forms for Fe-Co alloys in a wide range of concentrations. These alloys are predicted to have a stable tetragonal distortion, which in turn leads to an enhanced magnetocrystalline anisotropy energy of up to 0.75 MJ/m(3) and a saturated magnetization field of 1.9 T.

  • 20.
    Doe, Maofeng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Boström, Mathias
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Ultrathin nanosheet induced repulsive Casimir force with two transition pointsManuscript (preprint) (Other academic)
  • 21.
    Doe, Maofeng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. Department of Physics, University of Oslo, Norway .
    Analysis of the Semi local States in ZnO-InN Compounds2014In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 14, no 10, 4937-4943 p.Article in journal (Refereed)
    Abstract [en]

    ZnO alloys are extensively explored for the developments of optoelectronics. In this work we analyze the rather unconventional type of ZnO-based compound ZnOX (ZnO)(1y)Xy with X = InN. The compound forms alloy with ZnO and/or assembles cluster structures in the ZnO host. Importantly, this type of alloy benefits from being isovalent which implies a more stable crystalline structure, and at the same time it benefits from the oxynitride anion-alloying that alters the optoelectronic properties. Theoretical studies reveal that incorporating InN in ZnO strongly narrows the fundamental band gap energy Eg. For example, the (ZnO)(0.875)(InN)(0.125) alloy has the gap energy E-g = 2.20 eV = E-g(ZnO) 1.14 eV. The origin of this effect is a hybridization of the anion N 2p-like and O 2p-like orbitals. Intriguingly, the presence of InN nanoclusters enhances this effect and narrows the gap further, and moreover, the nanostructured configurations show more disperse energy distribution of the hybridized anion states compared with the random alloy. Nanoclustering affects the ZnO host more compared to structures with more random distribution of the InN dimers. On the basis of the different characters of the alloys and the nanostructures, we conclude that fine-tuned synthesizing of the (ZnO)(1-y)(InN)(y) alloys can be beneficial for a variety of novel nanosystems for optoelectronic and photoelectrochemical applications.

  • 22.
    Dou, Maofeng
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    First principles study of oxide semiconductors for solar energy applications2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The objectives of this thesis are to understand the electronic structures of oxides and oxynitrides for photocatalytic water splitting, examine the Casimir interaction between oxides, and explore possible approach to bridge the Casimir force and material properties for advanced material research. The studies were performed in the framework of the density functional theory, many-body perturbation theory, i.e, the GW approximation and Bethe-Salpeter equation, as well as the Casimir-Lifshitz approach.

    The thesis consists of two sets of results. In the first part (papers I-VI), the electronic structures of oxynitrides, i.e., ZnO-GaN and ZnO-InN, with different compositions and local structures have been studied. The oxynitrides reduce the band-gap energies significantly compared to the binary counterparts, enabling the oxynitrides to act as visible light active photocatalysts. Formation of cluster--like structures further reduces the band-gap and delocalizes the valence bands, benefiting higher optical absorption. Furthermore, the energy levels between oxynitride and water were aligned using a surface model adapted from semiconductor heterostructure.

    In the second part (papers V-IX), the electronic structures of oxides as well as the Casimir interactions have been examined. In particular, we investigated the differences of optical and electronic properties between SnO2 and TiO2 polymorphs in terms of band-edge characters and electron-phonon coupling. In addition, we synthesized a mesoporous material possessing two types of pore structures (one is hexagonal ordered with pore diameter of 2.60 nm and the other is disordered with pore diameter of 3.85 nm). The pore framework contains four-coordinated titanium and oxygen vacancies, verified by both experimental measurements and density-functional theory calculations. Utilizing the predicted properties of the materials, we studied the Casimir interactions. A stable equilibrium of Casimir force is achieved in planar geometry containing a thin film and porous substrates. Both the force and equilibrium distance are tuned through modification of the material properties, for instance, optical properties and porosity. Furthermore, we adapted this concept to study the interactions between gas bubbles and porous SiO2 in water. A transition from repulsion to attraction is predicted, which highlights that the bubbles may interact differently at different surface regions.

  • 23.
    Dou, Maofeng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Baldissera, Gustavo
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    ZnO-InN nanostructures with tailored photocatalytic properties for overall water-splitting2013In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 38, no 36, 16727-16732 p.Article in journal (Refereed)
    Abstract [en]

    ZnO-based electrodes for one-step photocatalytic water splitting are designed by incorporating InN. The electronic and optical properties of (ZnO)(1-x)(InN)(x) alloys and ZnO with InN-like cluster formations ZnO:(InN)(x) are analyzed by means of first-principles approaches. We calculate the energy gaps E-g, the band-edge energies relative to the vacuum level, and the optical absorption, employing the GW(o) method to describe single-particle excitations and the Bethe-Salpeter equation to model the two-particle exciton interactions. For ZnO and InN, the valence-band maximum (VBM) is E-VBM approximate to -7.3 and -5.7 eV, and the energy gap is E-g approximate to 3.3 and 0.7 eV, respectively. Incorporating InN into ZnO, the random (ZnO)(1-x)(InN)(x) alloys up-shifts the VBM and down-shifts the conduction-band minimum (CBM). In addition, the presence of InN-like clusters enhances this effect and significantly narrows the band gap. For instance, the VBM and the energy gap for 12.5% InN are E-VBM approximate to -6.5 and -6.1 eV, and E-g approximate to 2.2 and 1.9 eV for the alloy and the cluster structure, respectively. This impact on the electronic structure favors thus visible light absorption. With proper nanoclusters, the band edges straddle the redox potential levels of H+/H-2 and O-2/H2O, suggesting that ZnO-InN nanostructures can enhance the photocatalytic activity for overall solar-driven water splitting.

  • 24.
    Dou, Maofeng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Lou, Fei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Boström, Mathias
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Brevik, Iver
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Casimir quantum levitation tuned by means of material properties and geometries2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 20, 201407- p.Article in journal (Refereed)
    Abstract [en]

    The Casimir force between two surfaces is attractive in most cases. Although stable suspension of nano-objects has been achieved, the sophisticated geometries make them difficult to be merged with well-established thin film processes. We find that by introducing thin film surface coating on porous substrates, a repulsive to attractive force transition is achieved when the separations are increased in planar geometries, resulting in a stable suspension of two surfaces near the force transition separation. Both the magnitude of the force and the transition distance can be flexibly tailored though modifying the properties of the considered materials, that is, thin film thickness, doping concentration, and porosity. This stable suspension can be used to design new nanodevices with ultralow friction. Moreover, it might be convenient to merge this thin film coating approach with micro- and nanofabrication processes in the future.

  • 25.
    Dou, Maofeng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Yu, Tianhang
    Jin, Shengming
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Adjusting the Electronic and Optical Properties of Mesoporous MCM-41 Materials by Ti Doping2013In: Sensor Letters, ISSN 1546-198X, Vol. 11, no 8, 1530-1534 p.Article in journal (Refereed)
    Abstract [en]

    Solid mesoporous materials with ordered pore structures can be used for catalysis, genome sequencing, and drug delivering etc. The common method of synthesizing Ti doped mesoporous silica is to use costly ethyl silicate and tetrabutyl titanate as inorganic sources. In this work, however, low cost water glass and TiCl4 were used as the inorganic sources. Pore structures were studied by small angle X-ray diffraction, transmission electron microscopy, and N-2 adsorption-desorption. This Ti doped mesoporous material has binary mesopore structures with preferable pore sizes of 2.60 and 3.85 nm, respectively. Results from the ultraviolet-visible spectroscopy as well as density functional calculation employing a screened hybrid functional indicate that the mespore matrix contains tetrahedral coordinated Ti dopants (Ti-Si) and oxygen vacancies (V-O). The electron transitions from occupied V-O to the unoccupied Ti-Si contribute to the red-shift of the optical absorption edge. The hybrid potential describes fairly accurately the electronic structure and optical absorption, and we find an overall good qualitative agreement with the experimental characterization.

  • 26. Fiedler, Johannes
    et al.
    Thiyam, Priyadarshini
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. University of Oslo, Norway.
    Kurumbail, Anurag
    Burger, Friedrich A.
    Walter, Michael
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. University of Oslo, Norway.
    Brevik, Iver
    Parsons, Drew F.
    Bostrom, Mathias
    Buhmann, Stefan Y.
    Effective Polarizability Models2017In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 121, no 51, 9742-9751 p.Article in journal (Refereed)
    Abstract [en]

    Theories for the effective polarizability of a small particle in a medium are presented using different levels of approximation: we consider the virtual cavity, real cavity, and the hard-sphere models as well as a continuous interpolation of the latter two. We present the respective hard-sphere and-cavity radii as obtained from density-functional simulations as well as the resulting effective polarizabilities at discrete Matsubara frequencies. This enables us to account for macroscopic media in van der Waals interactions between molecules in water and their Casimir-Polder interaction with an interface.

  • 27. Gorbatov, O. I.
    et al.
    Gornostyrev, Y. N.
    Kuznetsov, A. R.
    Ruban, Andrei V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Effect of magnetism on short-range order formation in Fe-Si and Fe-Al alloys2011In: International Conference on Solid-Solid Phase Transformations in Inorganic Materials, PTM 2010, 2011, 618-623 p.Conference paper (Refereed)
    Abstract [en]

    Short-range order formation in dilute Fe-Si and Fe-Al alloys has been investigated by statistical Monte Carlo simulations with effective interactions deduced from first principles calculations for different magnetic structures of bcc Fe. We find that the variation of the magnetic order from ferromagnetic to paramagnetic leads to significant changes in effective cluster interactions and, as follow, in short-range order parameters of alloys. It is shown in agreement with experiment the B2 type short-range order is formed above the Curie temperature, TC, while the D03 type short-range order is preferred below TC.

  • 28.
    Gorbatov, Oleg I.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Flerskalig materialmodellering.
    Okatov, S. V.
    Gornostyrev, Yu N.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Ruban, Andrei V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Flerskalig materialmodellering.
    Effect of magnetism on the solubility of 3d elements in BCC iron: Results of first-principle investigations2013In: Physics of metals and metallography, ISSN 0031-918X, E-ISSN 1555-6190, Vol. 114, no 8, 642-653 p.Article in journal (Refereed)
    Abstract [en]

    The methods of quantum-mechanical simulation have been used to study alloys of bcc iron with 3d transition metals in the ferromagnetic and paramagnetic states. It has been shown that the main factor that determines the solubility of the 3d elements is their electronic structure. The energy of the solution, mixing, and effective interatomic interactions vary regularly depending on the position of the element in the Periodic Table and on the magnetic state of the matrix. In some cases, depending on the magnetic state, changes in these quantities lead to the violation of the Hume-Rothery rules that determine the solubility of substitutional elements in alloys. The results obtained help us to understand the microscopic mechanisms that determine the solubility of alloying elements and their effect on the phase stability and structural state of steels.

  • 29.
    Gorbatov, Oleg I.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Razumov, I. K.
    Gornostyrev, Yu N.
    Razumovskiy, Vsevolod I.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ruban, Andrei V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Role of magnetism in Cu precipitation in alpha-Fe2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 88, no 17, 174113- p.Article in journal (Refereed)
    Abstract [en]

    The temperature-dependent solubility of Cu in alpha-Fe and initial stages of Cu precipitation are investigated in first-principles calculations and statistical thermodynamic and kinetic modeling based on ab initio effective interactions. We demonstrate that the weakening of the phase separation tendency with increasing temperature, especially close to the magnetic phase transition, is related to the strong dependence of the "chemical" interactions on the global magnetic state. At the same time, our calculations demonstrate that the vibrational contribution obtained in the quasiharmonic approximation is relatively small for temperatures near the Curie point. The results of Monte Carlo simulations of Cu solubility and clustering are in good agreement with experimental data.

  • 30.
    Huang, Dan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Photocatalyst AgInS2 for active overall water-splitting: A first-principles study2014In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 591, 189-192 p.Article in journal (Refereed)
    Abstract [en]

    The electronic structure of photocatalyst AgInS2 has been investigated by first-principles calculation. Our results demonstrate that the band edge positions of chalcopyrite and orthorhombic AgInS2 straddle the water redox potentials. From the band offset calculation, we find that Ga-doping of AgInS2 shifts the conduction band minimum upwards, whereas Cu-doping of AgInS2 shifts the valence band maximum upwards. By (Ag,Cu)(In,Ga)S-2 alloying one can thereby tailor both the band edge positions and the band gap energy, and this effect provides an approach to optimize the band properties for overall water splitting.

  • 31.
    Huang, Dan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Ju, Zhiping
    Dou, Maofeng
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Yao, Chunmei
    Guo, Jin
    Investigation on AgGaSe2 for water splitting from first-principles calculations2014In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 105, no 3, 37007- p.Article in journal (Refereed)
    Abstract [en]

    The electronic structure of AgGaSe2 has been investigated as a photocatalyst candidate by first-principles calculation. Our results demonstrate that the band edge positions of bulk AgGaSe2 straddle the water redox potentials. From the band offset calculation, we find that Al-doping of AgGaSe2 shifts the conduction band minimum upwards, whereas Cu-doping of AgGaSe2 shifts the valence band maximum upwards. By (Ag, Cu)(Ga, Al)Se-2 alloying one can thereby tailor both the band edge positions and the band gap energy, and this effect provides an approach to optimize the band properties for overall water splitting. Moreover, AgGaSe2 forms a suitable junction with CuGaSe2 with a type-II band offset, which facilitates electron-hole separation. The AgGaSe2 and CuGaSe2 junction can be designed as a tandem photoelectrochemical device to improve the photocatalytic properties of the system.

  • 32. Kabliman, E.
    et al.
    Ruban, Andrei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Blaha, P.
    Schwarz, K.
    The atomic site occupancies in the Fe-Cr σ-phase2011In: 17th International Conference on Solid Compounds of Transition Elements, SCTE2010, 2011, 13-16 p.Conference paper (Refereed)
    Abstract [en]

    The atomic site distribution of the complex σ-phase structure (P42/mnm) has been studied using density functional theory (within the EMTO and WIEN2k codes) applying the cluster expansion method in a mean field approximation at finite temperatures. We found that at low temperatures Fe atoms predominantly occupy the icosahedrally coordinated (A,D) sites, Cr atoms prefer the (B,E) sites with the high coordination numbers, while the C site remains mixed. However, at higher temperature close to 1000 K all occupations become more and more mixed and reproduce well the available experimental data.

  • 33. Krivosheeva, A. V.
    et al.
    Shaposhnikov, V. L.
    Borisenko, V. E.
    Lazzari, J. -L
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Tay, B. K.
    Band gap modifications of two-dimensional defected MoS22015In: International Journal of Nanotechnology, ISSN 1475-7435, E-ISSN 1741-8151, Vol. 12, no 8-9, 654-662 p.Article in journal (Refereed)
    Abstract [en]

    The changes in structural and electronic properties, occurring in one monolayer of MoS<inf>2</inf> at different concentrations of oxygen atoms doping and vacancies are investigated by means of ab initio computer simulation. The substitution of sulphur atoms by oxygen ones reduces the band gap for high concentrations only, transforming direct-gap semiconductor into an indirect one, whereas a smaller concentration of oxygen practically does not influence the gap. The presence of sulphur vacancies strongly reduces the band gap, leading to bands overlapping at high concentration and appearance of new bands at the gap region, which are determined by Mo 4d states with the mixture of S 3p states, at low concentrations.

  • 34. Kulish, Vadym V.
    et al.
    Malyi, Oleksandr I.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. University of Oslo, Norway.
    Wu, Ping
    Adsorption of metal adatoms on single-layer phosphorene2015In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 2, 992-1000 p.Article in journal (Refereed)
    Abstract [en]

    Single- or few-layer phosphorene is a novel two-dimensional direct-bandgap nanomaterial. Based on first-principles calculations, we present a systematic study on the binding energy, geometry, magnetic moment and electronic structure of 20 different adatoms adsorbed on phosphorene. The adatoms cover a wide range of valences, including s and p valence metals, 3d transition metals, noble metals, semiconductors, hydrogen and oxygen. We find that adsorbed adatoms produce a rich diversity of structural, electronic and magnetic properties. Our work demonstrates that phosphorene forms strong bonds with all studied adatoms while still preserving its structural integrity. The adsorption energies of adatoms on phosphorene are more than twice higher than on graphene, while the largest distortions of phosphorene are only similar to 0.1-0.2 angstrom. The charge carrier type in phosphorene can be widely tuned by adatom adsorption. The unique combination of high reactivity with good structural stability is very promising for potential applications of phosphorene.

  • 35. Kulish, Vadym V.
    et al.
    Malyi, Oleksandr I.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. University of Oslo, Norway.
    Wu, Ping
    Phosphorene as an anode material for Na-ion batteries: a first-principles study2015In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 21, 13921-13928 p.Article in journal (Refereed)
    Abstract [en]

    We systematically investigate a novel two-dimensional nanomaterial, phosphorene, as an anode for Na-ion batteries. Using first-principles calculations, we determine the Na adsorption energy, specific capacity and Na diffusion barriers on monolayer phosphorene. We examine the main trends in the electronic structure and mechanical properties as a function of Na concentration. We find a favorable Na-phosphorene interaction with a high theoretical Na storage capacity. We find that Na-phosphorene undergoes semiconductor-metal transition at high Na concentration. Our results show that Na diffusion on phosphorene is fast and anisotropic with an energy barrier of only 0.04 eV. Owing to its high capacity, good stability, excellent electrical conductivity and high Na mobility, monolayer phosphorene is a very promising anode material for Na-ion batteries. The calculated performance in terms of specific capacity and diffusion barriers is compared to other layered 2D electrode materials, such as graphene, MoS2, and polysilane.

  • 36.
    Kumar, Mukesh
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Cu(Sb,Bi)(S,Se)2 as indium-free absorber material with high optical efficiency2014In: Energy Procedia: Volume 44, Pages 1-244 (2014) Proceedings of E-MRS Spring Meeting 2013 Symposium D Advanced Inorganic Materials and Structures for Photovoltaics 27-31 May 2013, Strasbourg, France, Elsevier, 2014, 176-183 p.Conference paper (Refereed)
    Abstract [en]

    Ternary Cu(Sb,Bi)(S,Se)2 compounds such as CuSbS2, CuSbSe2, CuBiS2, and CuBiSe2, are potential photovoltaic materials that contain earth abundant and low-cost elements. Employing an atomistic first-principles modeling within the density function theory we calculate the electronic and optical properties of Cu(Sb,Bi)(S,Se)2 compounds. We find that these four materials have indirect fundamental band gaps in the range of 1.1-1.7 eV. The indirect gap nature is different to the previous experimental measurements (direct gap). Calculations reveal that these materials have strong optical absorption compared to chalcopyrite CuIn(S,Se)2 and kesterite Cu2ZnSn(S,Se)4. The strong absorption of these compounds is explained by the localized p-states of cation Sb/Bi in the lower region of conduction band. Thereby, ternary Cu(Sb,Bi)(S,Se) 2 compounds have the potential to be used as absorber material in thin-film PV technologies.

  • 37.
    Kumar, Mukesh
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Zhao, Hanyue
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Study of band-structure, optical properties and native defects in A IBIIIO2 (AI = Cu or Ag, B III = Al, Ga or In) delafossites2013In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 28, no 6, 065003- p.Article in journal (Refereed)
    Abstract [en]

    In this work, employing a first-principles approach, the structural, electronic, optical, as well as the defect physics of AIB IIIO2 (AI = Cu or Ag, BIII = Al, Ga or In) compounds are discussed. We show that all these delafossite compounds have indirect band gaps with gap energy in the range = 1.6-3.6 eV. We also estimate the lowest direct band gap energies to be in the range = 2.6-4.0 eV. Optical characteristics reveal that AIBIIIO2 compounds exhibit a significant anisotropy for both the real and imaginary parts of the dielectric function. Furthermore, we find that absorption onset for these compounds is energetically well above (&gt;1.5 eV) the fundamental band gaps. Moreover, we demonstrate that the copper delafossites have larger absorption coefficients compared to the corresponding BIII cation silver delafossites in the visible range. Defect calculations reveal that Cu or Ag vacancy has the lowest formation energy followed by the O vacancy while the BIII cation vacancy has the highest formation energy.

  • 38.
    Leetmaa, M.a
    et al.
    Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Skorodumova, Natalia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    KMCLib 1.1: Extended random number support and technical updates to the KMCLib general framework for kinetic Monte-Carlo simulations2015In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 196, 611-613 p.Article in journal (Refereed)
    Abstract [en]

    We here present a revised version, v1.1, of the KMCLib general framework for kinetic Monte-Carlo (KMC) simulations. The generation of random numbers in KMCLib now relies on the C++11 standard library implementation, and support has been added for the user to choose from a set of C++11 implemented random number generators. The Mersenne-twister, the 24 and 48 bit RANLUX and a ’minimal-standard’ PRNG are supported. We have also included the possibility to use true random numbers via the C++11 std::random-device generator. This release also includes technical updates to support the use of an extended range of operating systems and compilers. New version program summary Program title: KMCLib v1.1 Catalogue identifier: AESZ-v1-1 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AESZ-v1-1.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 3 No. of lines in distributed program, including test data, etc.: 49,398 No. of bytes in distributed program, including test data, etc.: 1,536,855 Distribution format: tar.gz Programming language: Python and C++. Computer: Any computer that can run a C++11 compatible C++ compiler and a Python 2.7 interpreter. Operating system: Tested on Ubuntu 14.4 LTS, Ubuntu 12.4 LTS, CentOS 6.6, Mac OSX 10.10.3, Mac OSX 10.9.5 and Mac OSX 10.8.2 but should run on any system that can have a C++11 compatible C++ compiler and a Python 2.7 interpreter. Has the code been vectorized or parallelized?: Yes, with MPI. From one to hundreds of processors may be used depending on the type of input and simulation. RAM: From a few megabytes to several gigabytes depending on input parameters and the size of the system to simulate. Catalogue identifier of previous version: AESZ-v1-0 Journal reference of previous version: Comput. Phys. Comm. 185 (2014) 2340 Classification: 4.13, 16.13. External routines: To run the serial version of KMCLib no external libraries are needed other than the standard C++ runtime library and a Python 2.7 interpreter with support for numpy. For running the parallel version an MPI implementation is needed, such as e.g. MPICH from http://www.mpich.org or Open-MPI from http://www.open-mpi.org. SWIG (obtainable from http://www.swig.org/) and CMake (obtainable from http://www.cmake.org/) are both needed for building the backend module, while Sphinx (obtainable from http://sphinx-doc.org) is needed for building the documentation. CPPUNIT (obtainable from http://sourceforge.net/projects/cppunit/, also included in the KMCLib distribution) is needed for building the C++ unit tests Does the new version supersede the previous version?: Yes Nature of problem: Atomic scale simulation of slowly evolving dynamics is a great challenge in many areas of computational materials science and catalysis. When the rare-events dynamics of interest is orders of magnitude slower than the typical atomic vibrational frequencies a straight-forward propagation of the equations of motions for the particles in the simulation cannot reach time scales of relevance for modeling the slow dynamics. Solution method: KMCLib provides an implementation of the kinetic Monte Carlo (KMC) method that solves the slow dynamics problem by utilizing the separation of time scales between fast vibrational motion and the slowly evolving rare-events dynamics. Only the latter is treated explicitly and the system is simulated as jumping between fully equilibrated local energy minima on the slow-dynamics potential energy surface. Reasons for new version: The v1.1 revision increases the reliability and flexibility of the random number generation options in KMCLib, which is a central part of the KMC algorithm. The new release also comes with extended support for additional compilers and updates to the build system to simplify the installation procedure on some widely used platforms. Summary of revisions:Enough time has passed since the introduction of the <random> header in the C++ standard runtime library with the C++11 standard, that most installed compilers today have support to enable the use of C++11 specific language features in C+++. The <random> standard header comes with a set of well-defined pseudo random number generators (PRNG). Using standard library routines in favor of custom implementations has the obvious advantage of being more reliable and with guaranteed support over a longer time. From the v1.1 revision, KMCLib therefore relies on the C++11 standard library <random> header to produce pseudo-random numbers. This also makes it easier to enable support for several different PRNG:s for the user to choose from. From previously only supporting a Mersenne-twister implementation, KMCLib now has support for using the Mersenne-twister [1], the 24 and 48-bit RANLUX [2] generators, as well as a ’minimal-standard’ PRNG [3].For machines with a random device installed, KMCLib v1.1 can run simulations with true random numbers. This is enabled by using the std::random-device generator in C++. If the random device is properly installed the true random numbers are available to KMCLib out of the box and the user only needs to specify the use of the random device with an input flag in the same way as she chooses any of the available PRNG:s.The v1.1 revision includes major updates to the build system. The build system has no effect on the outcome of the simulations, but has a great impact on how easy it is to install the program. The Intel compiler is widely available on super computer clusters and support for this compiler widely extends the number of systems where KMCLib can be easily setup and run. The popularity of the Mac platform also makes smooth installation and compilation with clang desirable. With version v1.1 the make system for KMClib now includes support for the clang compiler on Mac and support for both the Intel compiler and the gcc compiler on Linux. See the reference manual for details of which versions of the operating systems and compilers have been tested.Restrictions: KMCLib implements the lattice KMC method and is as such, restricted to geometries that can be expressed on a grid in space. See the original paper describing KMCLib [4] for further details. Unusual features: KMCLib has been designed to be easily customized, to allow for user-defined functionality and integration with other codes. The user can define her own on-the-fly rate calculator via a Python API, so that site-specific elementary process rates, or rates depending on long-range interactions or complex geometrical features can easily be included. KMCLib also allows for on-the-fly analysis with user-defined analysis modules. KMCLib can keep track of individual particle movements and includes tools for mean square displacement analysis based on the algorithm described in Ref. [5], and is therefore particularly well suited for studying diffusion processes at surfaces and in solids. With the release of v1.1 KMCLib now supports several different pseudo random number generators, but can also, if a random device is installed on the machine, use true random numbers via the std::random-device generator. Additional comments: The full documentation of the program is distributed with the code and can also be found online at http://leetmaa.github.io/KMCLib/manual-v1.1/. Running time: From a few seconds to several days depending on the type of simulation and input parameters. References:M. Matsumoto and T. Nishimura, "Mersenne Twister: A 623- dimensionally equidistributed uniform pseudorandom number generator", ACM Trans. on Modeling and Computer Simulation, 8 (1998) 3.M. Lscher, "A portable high-quality random number generator for lattice field theory calculations", Computer Physics Communications, 79 (1994) 100110.S. K. Park, K. W. Miller and P K. Stockmeyer, "Technical correspondence", Communications of the ACM, 36 (1993) 105.M. Leetmaa and N. V. Skorodumova, "KMCLib: A general framework for lattice kinetic Monte Carlo (KMC) simulations", Computer Physics Communications, 185 (2014) 2340.M. Leetmaa and N. V. Skorodumova, "Mean square displacements with error estimates from non-equidistant time-step kinetic Monte Carlo simulations", Computer Physics Communications, 191 (2015) 119.

  • 39.
    Leetmaa, Mikael
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Skorodumova, Natalia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Kinetic Monte Carlo modelling of ion diffusion. Example: Ceria2013In: EFC 2013 - Proceedings of the 5th European Fuel Cell Piero Lunghi Conference, 2013, 53-54 p.Conference paper (Refereed)
    Abstract [en]

    Development of theoretical tools allowing us to study diffusion in solids at different scales is important for rational materials design. One of the effective approaches is a combination of Kinetic Monte Carlo technique with first principle electronic structure calculations. The KMClib program developed by us is a robust and flexible tool for studying diffusion, in particular, in ionconducting materials. The code has unique features such as on-thefly custom rate calculations, simulation of electrical bias and possibilities for on-the-fly analysis. It can be used in conjunction with ab initio calculations or just providing it with rates estimated from experiment or obtained in any other way. As an example of the code performance we present a simulation of oxygen diffusion in ceria.

  • 40.
    Leetmaa, Mikael
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. Department of Physics and Astronomy, Uppsala University.
    KMCLib: A general framework for lattice kinetic Monte Carlo (KMC) simulations2014In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 185, no 9, 2340-2349 p.Article in journal (Refereed)
    Abstract [en]

    KMCLib is a general framework for lattice kinetic Monte Carlo (KMC) simulations. The program can handle simulations of the diffusion and reaction of millions of particles in one, two, or three dimensions, and is designed to be easily extended and customized by the user to allow for the development of complex custom KMC models for specific systems without having to modify the core functionality of the program. Analysis modules and on-the-fly elementary step diffusion rate calculations can be implemented as plugins following a well-defined API. The plugin modules are loosely coupled to the core KMCLib program via the Python scripting language. KMCLib is written as a Python module with a backend C++ library. After initial compilation of the backend library KMCLib is used as a Python module; input to the program is given as a Python script executed using a standard Python interpreter. We give a detailed description of the features and implementation of the code and demonstrate its scaling behavior and parallel performance with a simple one-dimensional A-B-C lattice KMC model and a more complex three-dimensional lattice KMC model of oxygen-vacancy diffusion in a fluorite structured metal oxide. KMCLib can keep track of individual particle movements and includes tools for mean square displacement analysis, and is therefore particularly well suited for studying diffusion processes at surfaces and in solids. Program summary Program title: KMCLib Catalogue identifier: AESZ_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AESZ_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 3 No. of lines in distributed program, including test data, etc.: 49 064 No. of bytes in distributed program, including test data, etc.: 1 575 172 Distribution format: tar.gz Programming language: Python and C++. Computer: Any computer that can run a C++ compiler and a Python interpreter. Operating system: Tested on Ubuntu 12.4 LTS, CentOS release 5.9, Mac OSX 10.5.8 and Mac OSX 10.8.2, but should run on any system that can have a C++ compiler, MPI and a Python interpreter. Has the code been vectorized or parallelized?: Yes. From one to hundreds of processors depending on the type of input and simulation. RAM: From a few megabytes to several gigabytes depending on input parameters and the size of the system to simulate. Classification: 4.13, 16.13. External routines: KMCLib uses an external Mersenne Twister pseudo random number generator that is included in the code. A Python 2.7 interpreter and a standard C++ runtime library are needed to run the serial version of the code. For running the parallel version an MPI implementation is needed, such as e.g. MPICH from http://www.mpich.org or Open-MPI from http://www.open-mpi.org. SWIG (obtainable from http://www.swig.org/) and CMake (obtainable from http://www.cmake.org/) are needed for building the backend module, Sphinx (obtainable from http://sphinx-doc.org) for building the documentation and CPPUNIT (obtainable from http://sourceforge.net/projects/cppunit/) for building the C++ unit tests. Nature of problem: Atomic scale simulation of slowly evolving dynamics is a great challenge in many areas of computational materials science and catalysis. When the rare-events dynamics of interest is orders of magnitude slower than the typical atomic vibrational frequencies a straight-forward propagation of the equations of motions for the particles in the simulation cannot reach time scales of relevance for modeling the slow dynamics. Solution method: KMCLib provides an implementation of the kinetic Monte Carlo (KMC) method that solves the slow dynamics problem by utilizing the separation of time scales between fast vibrational motion and the slowly evolving rare-events dynamics. Only the latter is treated explicitly and the system is simulated as jumping between fully equilibrated local energy minima on the slow-dynamics potential energy surface. Restrictions: KMCLib implements the lattice KMC method and is as such restricted to geometries that can be expressed on a grid in space. Unusual features: KMCLib has been designed to be easily customized, to allow for user-defined functionality and integration with other codes. The user can define her own on-the-fly rate calculator via a Python API, so that site-specific elementary process rates, or rates depending on long-range interactions or complex geometrical features can easily be included. KMCLib also allows for on-the-fly analysis with user-defined analysis modules. KMCLib can keep track of individual particle movements and includes tools for mean square displacement analysis, and is therefore particularly well suited for studying diffusion processes at surfaces and in solids. Additional comments: The full documentation of the program is distributed with the code and can also be found at http://www.github.com/leetmaa/KMCLib/manual Running time: From a few seconds to several days depending on the type of simulation and input parameters.

  • 41.
    Leetmaa, Mikael
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. Uppsala University, Sweden.
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. Uppsala University, Sweden.
    Mean square displacements with error estimates from non-equidistant time-step kinetic Monte Carlo simulations2015In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 191, 119-124 p.Article in journal (Refereed)
    Abstract [en]

    We present a method to calculate mean square displacements (MSD) with error estimates from kinetic Monte Carlo (KMC) simulations of diffusion processes with non-equidistant time-steps. An analytical solution for estimating the errors is presented for the special case of one moving particle at fixed rate constant. The method is generalized to an efficient computational algorithm that can handle any number of moving particles or different rates in the simulated system. We show with examples that the proposed method gives the correct statistical error when the MSD curve describes pure Brownian motion and can otherwise be used as an upper bound for the true error.

  • 42. Li, X.
    et al.
    Bai, Y.
    Wang, B. C.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. University of Science and Technology Beijing, China.
    Su, Y. J.
    Water adsorption induced in-plane domain switching on BaTiO3 surface2015In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, no 9, 094104Article in journal (Refereed)
    Abstract [en]

    In this study, the influences of the adsorption of water molecules on the changes in the atomic and electric structures of BaTiO3 surface were investigated using ab initio calculation. Water molecules are molecularly and dissociatively adsorbed on the BaTiO3 surface, which makes electrons transfer from water molecules to the BaTiO3 surface. The redistribution of electrons in the BaTiO3 surface layers weakens the Ba-O interactions and strengthens the Ti-O interactions, so that the Ti atom shifts in TiO2 plane, i.e., an in-plane domain switching. The adsorption of water molecules on BaTiO3 surfaces also results in a reduction in the surface rumpling.

  • 43. Li, Xi
    et al.
    Wang, Baochang
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. University of Science and Technology Beijing, China.
    Zhang, Tong-Yi
    Su, Yanjing
    Water Adsorption and Dissociation on BaTiO3 Single-Crystal Surfaces2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 29, 15910-15918 p.Article in journal (Refereed)
    Abstract [en]

    Experimental and theoretical studies of water-molecule adsorption on BaTiO3 single-crystal surfaces are presented in this paper. The Fourier transform infrared spectrum shows that there are three types of energy-nonequivalent active modes for water-molecule adsorption on the in-plane-polarized BaTiO3(100) surface. The X-ray photoelectron spectroscopic results illustrate hydroxyl group on the surface, thereby indicating that the adsorbed water molecules are dissociated. The first-principles calculations of the 1/4-, 1/2-, and 1-monolayer water coverage demonstrate that H bonds are formed between the hydrogen of water and the surface oxygen of BaTiO3 and between the hydrogen of hydroxyl and the surface oxygen of BaTiO3, and the difference in the water adsorption behavior on the BaO- and TiO2-terminated surfaces. The calculation results are in good agreement with the experimental observations.

  • 44. Liang, Jie
    et al.
    Xia, Wei
    Sun, Junliang
    Su, Jie
    Dou, Maofeng
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Zou, Ruqiang
    Liao, Fuhui
    Wang, Yingxia
    Lin, Jianhua
    A multi-dimensional quasi-zeolite with 12 x 10 x 7-ring channels demonstrates high thermal stability and good gas adsorption selectivity2016In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 7, no 5, 3025-3030 p.Article in journal (Refereed)
    Abstract [en]

    A novel quasi-zeolite PKU-15, with a rare 3-dimensional structure containing interconnected large (12-ring), medium (10-ring) and small (7-ring) multi-pore channels, was hydrothermally synthesised and characterised. A unique tri-bridging O2- anion is found to be encapsulated in the cage-like (Ge,Si)(12)O-31 building unit and energetically stabilises the PKU-15 framework. The removal of this oxygen atom would convert PKU-15 into a hypothetical zeolite PKU-15H. Thus, PKU-15 can be considered as a unique 'quasi-zeolite', which bridges porous germanates and zeolites. Owing to the absence of terminal Ge-OH groups in its structure, PKU-15 shows a remarkably high thermal stability of up to 600 degrees C. PKU-15 is also the first microporous germanate that exhibits permanent porosity, with a BET area of 428 m(2) g(-1) and a good adsorption affinity toward CO2.

  • 45. Malyi, Oleksandr I.
    et al.
    Kulish, Vadym V.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. University of Oslo, Norway.
    In search of new reconstructions of (001) alpha-quartz surface: a first principles study2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 98, 55599-55603 p.Article in journal (Refereed)
    Abstract [en]

    Using Born-Oppenheimer molecular dynamics (BOMD) simulations and "static" density functional theory (DFT) calculations, the stability of cleaved and reconstructed alpha-SiO2(001) surfaces was studied. We found reconstructions ("dense", 2 x 2 reoptimized "dense", and 3 x 3 reoptimized "dense") which minimize the surface energy. The analysis of the surface energies shows that the cleaved surface reconstructs to the 2 x 2 reoptimized "dense" surface having a surface energy around 10% smaller than the "dense" surface. The results suggest that the optimization of Si-Si and Si-O distances at top surface layers plays the key role in stabilizing the 2 x 2 "dense" surface over the well-known "dense" surface.

  • 46. Migas, D. B.
    et al.
    Filonov, A. B.
    Borisenko, V. E.
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. Department of Physics and Astronomy, Uppsala University, Sweden.
    Orientation effects in morphology and electronic properties of anatase TiO2 one-dimensional nanostructures. II. Nanotubes2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 20, 9490-9498 p.Article in journal (Refereed)
    Abstract [en]

    In the first part [D. B. Migas et al., Phys. Chem. Chem. Phys., 2014, DOI: 10.1039/C3CP54988G] by means of ab initio calculations we have analyzed and discussed anisotropy effects on electronic properties of 001 -, 100 - and 110 - oriented anatase TiO2 nanowires. In this part we present results indicating crucial changes in morphology of anatase TiO2 nanotubes originating from TiO2 nanowires by making a hole along the wire axis. The critical wall thickness has been found to exist for the nanotubes with 001 and 110 axes: at smaller thickness their shape can be rounded, squeezed, viewed as conglomerates of nanocrystals and even represented as cylindrical and `single-walled'- like structures formed without rolling up a thin titania layer into a nanotube. In general, band dispersion near the gap region of TiO2 nanotubes is close to the one of TiO2 nanowires with the same orientation. We have also revealed that optimization of the unit cell parameter along the wire axis and consideration of quantum confinement and surface state effects are important to provide an interpretation of band-gap variation with respect to wall thickness in TiO2 nanotubes.

  • 47. Migas, D. B.
    et al.
    Shaposhnikov, V. L.
    Borisenko, V. E.
    Skorodumova, Natalia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. Uppsala University, Sweden.
    The surface energy and band structure of γWO3 thin films2017In: Science of Advanced Materials, ISSN 1947-2935, E-ISSN 1947-2943, Vol. 9, no 3-4, 469-474 p.Article in journal (Refereed)
    Abstract [en]

    By means of ab initio calculations we demonstrate sizable anisotropy in surface energy of the γWO3 (001), (010) and (100) surfaces. The (001) surface has the smallest surface energy followed by the (010) and (100) surfaces. Their surface band structures are characterized by dispersion of bands near the gap region and by band-gap values similar to the ones of the bulk. The role of surface atoms in stabilizing the band gap is revealed. Variations in the position of the Fermi level are traced with respect to the different surface reconstructions.

  • 48. Migas, D. B.
    et al.
    Shaposhnikov, V. L.
    Borisenko, V. E.
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    The Surface Energy and Band Structure of gamma-WO3 Thin Films2017In: Science of Advanced Materials, ISSN 1947-2935, E-ISSN 1947-2943, Vol. 9, no 3-4, 469-474 p.Article in journal (Refereed)
    Abstract [en]

    By means of ab initio calculations we demonstrate sizable anisotropy in surface energy of the gamma-WO3 (001), (010) and (100) surfaces. The (001) surface has the smallest surface energy followed by the (010) and (100) surfaces. Their surface band structures are characterized by dispersion of bands near the gap region and by band-gap values similar to the ones of the bulk. The role of surface atoms in stabilizing the band gap is revealed. Variations in the position of the Fermi level are traced with respect to the different surface reconstructions.

  • 49. Migas, Dmitri B.
    et al.
    Filonov, Andrew B.
    Borisenko, Victor E.
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Orientation effects in morphology and electronic properties of anatase TiO2 one-dimensional nanostructures. I. Nanowires2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 20, 9479-9489 p.Article in journal (Refereed)
    Abstract [en]

    By means of ab initio calculations we have revealed the existence of sizable anisotropy in electronic properties of anatase TiO2 nanowires with respect to orientation: nanowires with 001 , 100 and 110 axes are found to be direct band-gap, indirect band-gap and degenerate semiconductor materials, respectively. The degenerate semiconducting properties of 110 oriented TiO2 nanowires are predicted to be the intrinsic features closely connected with stoichiometry. A band-gap variation with nanowire diameter is also shown to display rather complex behavior characterized by a competition between quantum confinement and surface state effects that is fully compatible with the available contradictory experimental data. Finally, we propose a model to explain the band-gap variation with size in TiO2 nanowires, nanocrystals and thin films.

  • 50.
    Muhr, Sandra
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Aytekin, Kasim
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Woven steel mesh for usage in beds: A case study for IKEA2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study examines whether woven metal mesh is an appropriate option for usage in beds and what material the mesh should consist of to best be suited for the purpose. The woven steel mesh’s construction was based on a reference model that consists of cross-linked rods and wires.

    Since the aim of the project was to reach a conclusion of the mesh’s usability in beds, different parameters were examined and taken into consideration. These parameters were the durability of the mesh when carrying human weight, acoustic properties to minimize chatter when lying on the mesh and rolling properties.

    The durability was examined using COMSOL multiphysics. Acoustics were studied through a literature review and rolling properties were calculated using measurements on the reference model. A material investigation was done in the database software CES EduPack.

    It was found that steel, stainless steel and aluminum fulfilled the requirements set on durability. Stainless steel was considered too expensive and steel too heavy. Using aluminum halves the weight of the mesh in comparison to steel but doubles the price, in this case however the weight was considered to be a parameter of greater importance overriding price.

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