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  • 51.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Theoretical data for assessments2011Ingår i: Fundamentals of Thermodynamic Modelling of Materials, EDP Sciences, 2011, Vol. 14, s. 03003-Konferensbidrag (Refereegranskat)
  • 52.
    Korzhavyi, Pavel A.
    et al.
    Uppsala University.
    Abrikosov, I. A.
    Uppsala University.
    Johansson, Börje
    Uppsala University.
    Ruban, A. V.
    Technical University of Denmark.
    Skriver, H. L.
    Technical University of Denmark.
    First-principles calculations of the vacancy formation energy in transition and noble metals1999Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 59, nr 18, s. 11693-11703Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The vacancy formation energy and the vacancy formation volume of the 3d, 4d, and 5d transition and noble metals have been calculated within the local-density approximation. The calculations employ the order-N locally self-consistent Green’s-function method in conjunction with a supercell approach and include electrostatic multipole corrections to the atomic sphere approximation. The results are in excellent agreement with available full-potential calculations and with the vacancy formation energies obtained in positron annihilation measurements. The variation of the vacancy formation energy through a transition-metal series and the effects of crystal and magnetic structure are investigated and discussed.

  • 53.
    Korzhavyi, Pavel A.
    et al.
    KTH, Tidigare Institutioner, Materialvetenskap.
    Abrikosov, I. A.
    Smirnova, E. A.
    Bergqvist, L.
    Mohn, P.
    Mathieu, R.
    Svedlindh, P.
    Sadowski, J.
    Isaev, E. I.
    Vekilov, Y. K.
    Eriksson, O.
    Defect-induced magnetic structure in (Ga1-xMnx)As2002Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 88, nr 18, s. 187202-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We show that magnetic structures involving partial disorder of local magnetic moments on the Mn atoms in (Ga1-xMnx)As lower the total energy, compared to the case of perfect ferromagnetic ordering, when As defects on the Ga sublattice are present. Such magnetic structures are found to be stable for a range of concentrations of As antisites, and this result accounts for the observed magnetic moments and critical temperatures in (Ga1-xMnx)As . We propose an explanation for the stabilization of the partially disordered magnetic structures and conclude that the magnetization and critical temperatures should increase substantially by reducing the number of As antisite defects.

  • 54.
    Korzhavyi, Pavel A.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Thermodynamic properties of copper compounds with oxygen and hydrogen from first principles2010Rapport (Refereegranskat)
    Abstract [en]

    We employ quantum-mechanical calculations (based on density functional theory and linear response theory) in order to test the mechanical and chemical stability of several solid-state configurations of Cu1+, Cu2+, O2–, H1–, and H1+ ions. We begin our analysis with cuprous oxide (Cu2O, cuprite structure), cupric oxide (CuO, tenorite structure), and cuprous hydride (CuH, wurtzite and sphalerite structures) whose thermodynamic properties have been studied experimentally. In our calculations, all these compounds are found to be mechanically stable configurations. Their formation energies calculated at T = 0 K (including the energy of zero-point and thermal motion of the ions) and at room temperature are in good agreement with existing thermodynamic data. A search for other possible solid-state conformations of copper, hydrogen, and oxygen ions is then performed. Several candidate structures for solid phases of cuprous oxy-hydride (Cu4H2O) and cupric hydride (CuH2) have been considered but found to be dynamically unstable. Cuprous oxy-hydride is found to be energetically unstable with respect to decomposition onto cuprous oxide and cuprous hydride. Metastability of cuprous hydroxide (CuOH) is established in our calculations. The free energy of CuOH is calculated to be some 50 kJ/mol higher than the average of the free energies of Cu2O and water. Thus, cuprite Cu2O is the most stable of the examined Cu(I) compounds.

  • 55.
    Korzhavyi, Pavel A.
    et al.
    KTH, Tidigare Institutioner, Materialvetenskap.
    Pourovskii, Leonid V.
    Department of Physics, Uppsala University.
    Hugosson, Håkan W.
    Department of Physics, Uppsala University.
    Ruban, Andrei V.
    Department of Physics, Technical University of Denmark.
    Johansson, Börje
    KTH, Tidigare Institutioner, Materialvetenskap.
    Ab Initio Study of Phase Equilibria in TiCx2002Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 88, nr 1, s. 015505-1-01505-4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The phase diagram for the vacancy-ordered structures in the substoichiometric TiCx (x=0.5-1.0) has been established from Monte Carlo simulations with the long-range pair and multisite effective interactions obtained from ab initio calculations. Three ordered superstructures of vacancies (Ti2C, Ti3C2, and Ti6C5) are found to be ground state configurations. Their stability has been verified by full-potential total energy calculations of the fully relaxed structures.

  • 56.
    Korzhavyi, Pavel A.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Ruban, Andrei
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Odqvist, J.
    Nilsson, J.-O.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Electronic structure and effective chemical and magnetic exchange interactions in bcc Fe-Cr alloys2009Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, nr 5, s. 054202-Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Electronic structure calculations are employed in order to investigate the cohesive properties (lattice parameter, enthalpy of formation, and bulk modulus) of random Fe-Cr alloys as a function of composition and magnetic state, as well as to derive the chemical and magnetic exchange interactions of the constituent atoms. The calculations predict certain anomalies in the cohesive properties of ferromagnetic alloys at a concentration of about 7 at % Cr; these anomalies may be related to the changes in Fermi-surface topology that occur with composition in this alloy system. The obtained interatomic interactions are used as parameters in the configurational (Ising) and magnetic (Heisenberg) Hamiltonians for modeling finite-temperature thermodynamic properties of the alloys. We discuss the approximations and limitations of similar modeling approaches, investigate the origin of existing difficulties, and analyze possible ways of extending the theoretical models in order to capture the essential physics of interatomic interactions in the Fe-Cr or similar alloys where magnetism plays a crucial role in the phase stability.

  • 57.
    Korzhavyi, Pavel A.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Ruban, Andrei V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    First-principles calculations as a new tool in steel research2008Ingår i: 6th European Stainless Steel Conference, Science and Market Helsinki, Finland, June 10-13, 2008: Proceedings / [ed] P. Karjalainen and S. Hertzman, Jernkontoret , 2008, s. 279-284Konferensbidrag (Refereegranskat)
    Abstract [en]

    Great scepticism over the earliest applications of the first-principles theory to the calculation of the ground state properties of real systems in the 70’s and 80’s has gradually turned into a widespread belief in its quantitative accuracy and predictive power, due to a great number of successful applications to very different systems and problems, so that several leading materials manufacturing companies have initiated first-principles based research programs aimed at design of new materials. However, the role of first-principles calculations in the design process, and, most importantly, their potential, remain quite obscure. We therefore try to give a “balanced” view on the possibilities of first-principles calculations, not only telling success stories, but also discussing their problems and limitations. Then, we demonstrate uniqueness of the information that can be obtained using first-principles methods. Thus we determine their place among the traditional research methods and tools in materials science. In order to show the capabilities of first-principles calculations, we present some recent applications of first-principles methods to investigation of the thermodynamic and kinetic properties of austenitic (including high-nitrogen) and ferritic steels, at the atomic level. Finally, we indicate problems, related to steel research and development, where first-principles methods (together with other experimental or theoretical techniques) can lead to substantial progress or even breakthroughs.

  • 58.
    Korzhavyi, Pavel A.
    et al.
    Uppsala University.
    Ruban, Andrei V.
    Technical University of Denmark.
    Lozovoi, A. Y.
    Vekilov, Y. K.
    Abrikosov, I. A.
    Johansson, Börje
    Uppsala University.
    Constitutional and thermal point defects in B2 NiAl2000Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 61, nr 9, s. 6003-6018Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The formation energies of point defects and the interaction energies of various defect pairs in NiAl are calculated from first principles within an order N, locally self-consistent Green's-function method in conjunction with multipole electrostatic corrections to the atomic sphere approximation. The theory correctly reproduces the ground state for the off-stoichiometric NiAl alloys. The constitutional defects (antisite Ni atoms and Ni vacancies in Ni-rich and Al-rich NiAl, respectively) are shown to form ordered structures in the ground state, in which they tend to avoid each other at the shortest distance on their sublattice. The dominant thermal defects in Ni-rich and stoichiometric NiAl are calculated to be triple defects. In Al-rich alloys another type of thermal defect dominates, where two Ni vacancies are replaced by one antisite Al atom. As a result, the vacancy concentration decreases with temperature in this region. The effective defect formation enthalpies for different concentration regions of NiAl are also obtained.

  • 59.
    Korzhavyi, Pavel A.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Sandström, Rolf
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    First-principles evaluation of the effect of alloying elements on the lattice parameter of a 23Cr25NiWCuCo austenitic stainless steel to model solid solution hardening contribution to the creep strength2015Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 626, s. 213-219Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By the use of first-principles calculations based on density functional theory, lattice misfit parameters for alloying elements in the austenitic stainless steel 23Cr25NiWCuCo have been derived. These lattice misfit parameters have been applied to determine the solid solution hardening of the elements W, Nb, and Cu in the steel. The model for solid solution hardening is based on work by Hirth and Lothe, where solutes are creating Cottrell clouds around the dislocations and slow down their motion. The model is also verified by comparison to creep tests for Ni-20%Cr and Ni-20%Cr-6W, where W is almost completely in solid solution and no other strengthening mechanism than solid solution hardening should be active. The contribution from the interstitial elements C and N to the solid solution hardening is found to be negligibly small for the studied steel.

  • 60.
    Korzhavyi, Pavel A.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Soroka, Inna
    Uppsala Universitet.
    Boman, Mats
    Uppsala Universitet.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Thermodynamics of stable and metastable Cu-O-H compounds2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    We apply density functional perturbation theory together with experimental studies in order to investigate the structure and physical properties of possible stable and metastable copper(I) compounds with oxygen and hydrogen. Copper(I) hydride, CuH, is found to be a metastable phase which decomposes at ambient conditions and exhibiting a semiconducting gap in the electronic spectrum. The calculated structure and phonon spectra are found to be in good agreement with experimental data. The phonon spectra of a novel metastable phase, copper(I) hydroxide, are also determined.

  • 61.
    Korzhavyi, Pavel A.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Soroka, Inna L.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi.
    Isaev, Eyvaz I.
    Lilja, Christina
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Exploring monovalent copper compounds with oxygen and hydrogen2012Ingår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 109, nr 3, s. 686-689Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    New important applications of copper metal, e.g., in the areas of hydrogen production, fuel cell operation, and spent nuclear fuel disposal, require accurate knowledge of the physical and chemical properties of stable and metastable copper compounds. Among the copper(I) compounds with oxygen and hydrogen, cuprous oxide Cu(2)O is the only one stable and the best studied. Other such compounds are less known (CuH) or totally unknown (CuOH) due to their instability relative to the oxide. Here we combine quantum-mechanical calculations with experimental studies to search for possible compounds of monovalent copper. Cuprous hydride (CuH) and cuprous hydroxide (CuOH) are proved to exist in solid form. We establish the chemical and physical properties of these compounds, thereby filling the existing gaps in our understanding of hydrogen- and oxygen-related phenomena in Cu metal.

  • 62.
    Korzhavyi, Pavel A.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sundman, Bo
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Selleby, Malin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Atomic, electronic, and magnetic structure of iron-based sigma-phases2005Ingår i: Integrative and Interdisciplinary Aspects of Intermetallics / [ed] MIlls, MJ; Inui, H; Clemens, H; Fu, CL, WARRENDALE: MATERIALS RESEARCH SOCIETY , 2005, Vol. 842, s. 517-522Konferensbidrag (Refereegranskat)
    Abstract [en]

    A combination of ab initio total energy calculations with Calphad approach is applied to model the site occupancy and thermodynamic properties of the Fe-Cr, Co-Cr, Fe-V, and Fe-Mo binary sigma-phases as a function of composition and temperature. For each binary sigma-phase the parameters of the model are the ab initio calculated total energies of so-called end-member compounds, which represent all the 2(5)=32 variants of complete occupancy of each of the five crystallographically inequivalent sites by one or the other alloy component, The paramagnetic state of the sigma-phases has been taken into account within the disordered local moment approach. The Fe and Co atoms are found to retain high spin moments when they occupy high-coordination-number sites in the structure. Using our model we were able to reproduce the experimentally observed site occupancy in the FeCr sigma-phase. The calculated site occupancies in the Co-Cr, Fe-V, and Fe-Mo sigma-phases are also presented and discussed.

  • 63.
    Korzhavyi, Pavel A.
    et al.
    KTH, Tidigare Institutioner, Materialvetenskap.
    Vitos, Levente
    KTH, Tidigare Institutioner, Materialvetenskap.
    Andersson, David A.
    KTH, Tidigare Institutioner, Materialvetenskap.
    Johansson, Börje
    KTH, Tidigare Institutioner, Materialvetenskap.
    Oxidation of plutonium dioxide2004Ingår i: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 3, nr 4, s. 225-228Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The physics and chemistry of the actinide elements form the scientific basis for rational handling of nuclear materials(1-3). In recent experiments(4), most unexpectedly, plutonium dioxide has been found to react with water to form higher oxides up to PuO2.27, whereas PuO2 had always been thought to be the highest stable oxide of plutonium(2,3). We perform a theoretical analysis of this complicated situation on the basis of total energies calculated within density functional theory(5,6) combined with well-established thermodynamic data. The reactions of PuO2 with either O-2 or H2O to form PuO2+delta are calculated to be endothermic: that is, in order to occur they require a supply of energy. However, our calculations show that PuO2+delta can be formed, as an intermediate product, by reactions with the products of radiolysis of water, such as H2O2.

  • 64.
    Korzhavyi, Pavel A.
    et al.
    KTH, Tidigare Institutioner, Materialvetenskap.
    Vitos, Levente
    KTH, Tidigare Institutioner, Materialvetenskap.
    Johansson, Börje
    KTH, Tidigare Institutioner, Materialvetenskap.
    Thermodynamic properties of Pu-O-H compounds and alloys from density functional theory2004Ingår i: SCIENTIFIC BASIS FOR NUCLEAR WASTE MANAGEMENT XXVII / [ed] Oversby, VM; Werme, LO, WARRENDALE: Materials Research Society, 2004, Vol. 807, s. 107-112Konferensbidrag (Refereegranskat)
    Abstract [en]

    A theoretical approach has been developed that allows one to obtain thermodynamic properties of plutonium-based alloys and compounds from first-principles electronic structure calculations based on density functional theory. The approach is applied to study the defect structure in non-stoichiometric PuO2+/-delta.

  • 65. Körmann, Fritz
    et al.
    Breidi, Abed Al Hasan
    Dudarev, Sergei L.
    Dupin, Nathalie
    Ghosh, Gautam
    Hickel, Tilmann
    Korzhavyi, Pavel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Munoz, Jorge A.
    Ohnuma, Ikuo
    Lambda transitions in materials science: Recent advances in CALPHAD and first-principles modelling2014Ingår i: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 251, nr 1, s. 53-80Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper provides a comprehensive overview of state-of-the-art computational techniques to thermodynamically model magnetic and chemical order-disorder transitions. Recent advances as well as limitations of various approaches to these so-called lambda transitions are examined in detail, focussing on calphad models and first-principles methods based on density functional theory (DFT). On the one hand empirical implementations -based on the Inden-Hillert-Jarl formalism -are investigated, including a detailed interpretation of the relevant parameters, physical limiting cases and potential extensions. In addition, Bragg-Williams-based approaches as well as cluster-variation methods of chemical order-disorder transitions are discussed. On the other hand, it is shown how magnetic contributions can be introduced based on various microscopic model Hamiltonians (Hubbard model, Heisenberg model and beyond) in combination with DFT-computed parameters. As a result of the investigation we were able to indicate similarities between the treatment of chemical and magnetic degrees of freedom as well as the treatment within the calphad and DFT approaches. Potential synergy effects resulting from this overlap have been derived and alternative approaches have been suggested, in order to improve future thermodynamic modelling of lambda transitions.

  • 66.
    Li, Yunguo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Physical and chemical properties of Cu(I) compounds with O and/or H2017Ingår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, nr 2, s. 529-538Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electronic structure and chemical bonding of Cu(I) compounds with O and/or H are investigated using ab initio calculations based on density functional theory. A hybrid functional PBE0 is employed, which accurately reproduces an experimental band gap of cuprite Cu2O. Cuprous hydroxide CuOH (cuprice) is found to be an indirect band gap semiconductor. Depending on the bond network configuration of CuOH, its band gap is found to vary between 2.73 eV and 3.03 eV. The presence of hydrogen in CuOH has little effect on the character of Cu-O bonds, as compared to Cu2O, but lowers the energy levels of the occupied states upon O- H bond formation. The bonding charge density and electron localization function calculations reveal that a closed-shell Cu-Cu interaction takes place in Cu2O and CuOH between the neighbouring Cu cations belonging to different bond networks. Besides, three structures of cuprous hydride CuH are investigated. We find that the halite structure of CuH can be stabilized at high pressure (above 32 GPa) while wurtzite is the most stable structure of CuH at ambient pressure. The H-H interaction contributes to the dynamical stabilization of the halite structure. The wurtzite and sphalerite structures of CuH are predicted to be semiconducting with small band gaps, while the halite structure is calculated to be metallic.

  • 67.
    Li, Yunguo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sandström, Rolf
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Lilja, Christina
    Impurity effects on the grain boundary cohesion in copper2017Ingår i: Physical Review Materials, ISSN 2475-9953, Vol. 1, nr 7, artikel-id 070602Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Segregated impurities at grain boundaries can dramatically change the mechanical behavior of metals, while the mechanism is still obscure in some cases. Here, we suggest a unified approach to investigate segregation and its effects on the mechanical properties of polycrystalline alloys using the example of 3sp impurities (Mg, Al, Si, P, or S) at a special type Sigma 5(310)[001] tilt grain boundary in Cu. We show that for these impurities segregating to the grain boundary, the strain contribution to the work of grain boundary decohesion is small and that the chemical contribution correlates with the electronegativity difference between Cu and the impurity. The strain contribution to the work of dislocation emission is calculated to be negative, while the chemical contribution is calculated to be always positive. Both the strain and chemical contributions to the work of dislocation emission generally become weaker with the increasing electronegativity from Mg to S. By combining these contributions together, we find, in agreement with experimental observations, that a strong segregation of S can reduce the work of grain boundary separation below the work of dislocation emission, thus embrittling Cu, while such an embrittlement cannot be produced by a P segregation because it lowers the energy barrier for dislocation emission relatively more than for work separation.

  • 68.
    Li, Yunguo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Interactions of point defects with stacking faults in oxygen-free phosphorus-containing copper2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 462, s. 160-164Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The interactions of stacking faults and point defects in oxygen-free phosphorus-containing copper are investigated using ab initio methods. Although monovacancies can act as traps for H impurities or OH groups, the calculations show that two vacancies only weakly bind with each other and this interaction terminates at the third nearest-neighbor distance. An interstitial P tends to form a Cu-P dumbbell-like cluster around the lattice site and can readily combine with a vacancy to become a substitutional impurity. It is also found that the intrinsic stacking-fault energy of copper strongly depends on the temperature as well as on the presences of point defects. The intrinsic stacking-fault energy varies between 20 and 77 mJ/m2 depending on the presence of point defects in the faulted region. These point defects are also found to affect the unstable stacking-fault energy, but they always increase the twinning tendency of copper. Among them, the substitutional P is found to have the strongest effects, decreasing the intrinsic stacking-fault energy and increasing the twinnability.

  • 69.
    Li, Yunguo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Physcico-chemical Properties of Cu(I) Compounds with O and/or HManuskript (preprint) (Övrigt vetenskapligt)
  • 70.
    Li, Yunguo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Lousada, Claudio Miguel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    The nature of hydrogen in gamma-alumina2014Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, nr 20, s. 203514-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gibbs free energy models are derived from the calculated electronic and phonon structure of two possible models of gamma-alumina, a defective spinel phase and a hydrogenated spinel phase. The intrinsic vacancies and hydrogen in the two structural models give rise to a considerable configurational (residual) entropy and significantly contribute to thermodynamic stability and physical-chemical properties of gamma-alumina, which was neglected in previous studies but considered in this work. The electronic densities of states, calculated using a hybrid functional for the two structural models of gamma-alumina, are presented. The dynamic stability of the two phases is confirmed by full-spectrum phonon calculations. The two phases share many similarities in their electronic structure, but can be distinguished by their vibrational spectra and specific heat. The defective spinel is found to be the ground state of gamma-alumina, while the hydrogenated spinel to be a metastable phase. However, dehydration of the metastable phase into the ground state is expected to be slow due to the low diffusion rate of H, which leaves hydrogen as a locked-in impurity in gamma-alumina.

  • 71.
    Li, Yunguo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Lousada, Claudio Miguel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Soroka, Inna L.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Bond Network Topology and Antiferroelectric Order in Cuprice CuOH2015Ingår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 54, nr 18, s. 8969-8977Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using density functional theory (DFT) and a graph theory based approach, we investigated the topology of bond network in CuOH(s) (cuprice) considering only symmetry-distinct structures. In parallel, we conducted the synthesis and X-ray diffraction characterization of the compound and used the combined theoretical-experimental effort to validate the lowest energy structure obtained with DFT. The ground-state structure of CuOH(s) consists of compact trilayers of CuOH connected to each other via hydrogen bonds, where the inner layer of each trilayer is composed entirely of Cu atoms. Each trilayer is a dense fabric made of two interlocked arrays of polymer [CuOH]<inf>n</inf> chains. This structure corresponds to an antiferroelectric configuration where the dipole moments of CuOH molecules belonging to adjacent arrays are antiparallel and are arranged in the same way as the water molecules in ice-VIII. It is shown that a collective electrostatic interaction is the main driving force for the cation ordering while the local atomic configuration is maintained. These findings and the possibility of synthesizing exfoliated two-dimensional cuprice are important for some technological applications.

  • 72.
    Li, Yunguo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Lousada, Cláudio M.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Soroka, Inna L.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Bonding Topology and Antiferroelectric Order in Cuprice, CuOHManuskript (preprint) (Övrigt vetenskapligt)
  • 73.
    Li, Yunguo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Lousada, Cláudio M.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Soroka, Inna L.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Cation Ordering in Cuprice, CuOH2015Ingår i: Proceedings of PTM 2015, 2015Konferensbidrag (Övrigt vetenskapligt)
  • 74.
    Li, Yunguo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Lousada, Patricio Claudio Miguel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Korzhavy, Pavel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Electronic structures and optical properties of cuprous oxide and hydroxide2014Ingår i: Materials Research Society Symposium Proceedings, ISSN 0272-9172, E-ISSN 1946-4274, Vol. 1675, s. 185-190Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The broad range of applications of copper, including areas such as electronics, fuel cells, and spent nuclear fuel disposal, require accurate description of the physical and chemical properties of copper compounds. Within some of these applications, cuprous hydroxide is a compound whose relevance has been recently discovered. Its existence in the solid-state form was recently reported. Experimental determination of its physical-chemical properties is challenging due to its instability and poop crystallinity. Within the framework of density functional theory calculations (DFT), we investigated the nature of bonding, electronic spectra, and optical properties of the cuprous oxide and cuprous hydroxide. It is found that the hybrid functional PBEO can accurately describe the electronic structure and optical properties of these two copper(I) compounds. The calculated properties of cuprous oxide are in good agreement with the experimental data and other theoretical results. The structure of cuprous hydroxide can be deduced from that of cuprous oxide by substituting half Cu∗ in Cu2O lattice with protons. Compared to CU2O, the presence of hydrogen in CuOH has little effect on the ionic nature of Cu-O bonding, but lowers the energy levels of the occupied states. Thus, CuOH is calculated to have a wider indirect band gap of 2.73 eV compared with the Cu2O band gap of 2.17 eV.

  • 75.
    Li, Yunguo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Sandström, Rolf
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Defect Chemistry and Ductile-to-brittle Transition in Polycrystalline Cu MetalManuskript (preprint) (Övrigt vetenskapligt)
  • 76.
    Li, Zhou
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Mao, Huahai
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    Korzhavy, Pavel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    Selleby, Malin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    Thermodynamic re-assessment of the Co-Cr system supported by first-principles calculations2016Ingår i: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 52, s. 1-7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The phase equilibria and thermochemical properties of the Co-Cr system was re-assessed using the Calphad method with the aid of ab initio calculations. Four solution phases, liquid, bcc, fcc and hcp phases are modeled using the substitutional solution model. The sigma phase, as an intermetallic compound with certain homogeneous composition range, is modeled by a full five sublattices partitioned CEF model. The formation enthalpies of all end-members are obtained from ab initio calculations. The calculated results fit the experimental data reasonably well which indicates that this ab initio aided model is a proper description for the sigma phase.

  • 77.
    Lousada, Claudio M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Johansson, A. J.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Adsorption of Hydrogen Sulfide, Hydrosulfide and Sulfide at Cu(110) - Polarizability and Cooperativity Effects. First Stages of Formation of a Sulfide Layer2018Ingår i: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 19, nr 17, s. 2159-2168Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Understanding the surface site preference for single adsorbates, the interactions between adsorbates, how these interactions affect surface site specificity in adsorption and perturb the electronic states of surfaces is important for rationalizing the structure of interfaces and the growth of surface products. Herein, using density functional theory (DFT) calculations, we investigated the adsorption of H2S, HS and, S onto Cu(110). The surface site specificity observed for single adsorbates can be largely affected by the presence of other adsorbates, especially S that can affect the adsorption of other species even at distances of 13 Å. The large supercell employed with a surface periodicity of (6×6) allowed us to safely use the Helmholtz method for the determination of the dipole of the surface-adsorbate complex at low adsorbate coverages. We found that the surface perturbation induced by S can be explained by the charge transfer model, H2S leads to a perturbation of the surface that arises mostly from Pauli exclusion effects, whereas HS shows a mix of charge transfer and Pauli exclusion effects. These effects have a large contribution to the long range adsorbate-adsorbate interactions observed. Further support for the long range adsorbate-adsorbate interactions are the values of the adsorption energies of adsorbate pairs that are larger than the sum of the adsorption energies of the single adsorbates that constitute the pair. This happens even for large distances and thus goes beyond the H-bond contribution for the H-bond capable adsorbate pairs. Exploiting this knowledge we investigated two models for describing the first stages of growth of a layer of S-atoms at the surface: the formation of islands versus the formation of more homogeneous surface distributions of S-atoms. We found that for coverages lower than 0.5 ML the S-atoms prefer to cluster as islands that evolve to stripes along the [1 (Formula presented.) 0] direction with increasing coverage. At 0.5 ML a homogeneous distribution of S-atoms becomes more stable than the formation of stripes. For the coverage equivalent to 1 ML, the formation of two half-monolayers of S-atoms that disrupt the Cu−Cu bonds between the first and second layer is more favorable than the formation of 1 ML homogeneous coverage of S-atoms. Here the S−Cu bond distances and geometries are reminiscent of pyrite, covellite, and to some extent chalcocite. The small energy difference of ≈0.1 eV that exists between this structure and the formation of 1 ML suggests that in a real system at finite temperature both structures may coexist leading to a structure with even lower symmetry.

  • 78.
    Lousada, Claudio M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    First stages of oxide growth on Al(1 1 0) and core-level shifts from density functional theory calculations2018Ingår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 441, s. 174-186Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The formation of islands of O-atoms is the dominant mode of growth of the oxide in the first stages of oxidation of Al(1 1 1). It is however unknown if a similar mechanism exists for other low index surfaces of Al. We performed a density functional theory (DFT) and ab initio molecular dynamics investigation of the first stages of the oxidation of Al(1 1 0) using two distinct models: a homogeneous surface disposition of O-atoms; and a model where the O-atoms are close-spaced forming clusters or islands. We investigated the surface reactions with oxygen up to a coverage of 2 ML and found that for both models the adsorption energy per dissociating O2(g) becomes more negative with increasing coverage. Our results show that for coverages up to 1.25 ML the oxide forms clusters or islands while for coverages higher than 1.5 ML the oxide covers the surface homogeneously. This is because the O-atoms bind preferably to neighboring sites even at the minimum coverage. With increasing coverage, the clusters of O start to form stripes along the [1 1¯ 0] direction. The work function (ϕ) of the surface decreases when going from bare Al(1 1 0) to up to 1 ML coverage of O-atoms, but for coverages of 1.25 ML and higher, ϕ increases. The Al 2p surface core level shifts (SCLS) shift towards higher binding energies with increasing surface coverage of O-atoms and start to approach the values of Al 2p in Al2O3 already at a coverage of 2ML. A relation between the SCLS and the coordination number of Al to O-atoms was made. The Al 2p SCLS increases with increasing coordination to O-atoms, for single, twofold and three-fourfold coordinated cations. For the O-atoms that terminate the surface at the short-bridge sites, the SCLS of O 1s, is largely affected by the proximity to other O-atoms. These results demonstrate that the cooperative effects between surface bound O-atoms have important roles in the mechanism of growth of the oxide at Al(1 1 0), and similarly to what happens for Al(1 1 1), the initial oxidation of Al(1 1 0) proceeds via the formation of islands of O-atoms.

  • 79.
    Lousada, Claudio M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi. RAS, Ural Div, Inst Met Phys, Ekaterinburg 620219, Russia..
    The first stages of oxide growth at the low index Al surfaces (100), (110), (111): clusters and stripes vs. homogeneous growth2018Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, nr 46, s. 29549-29557Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We performed a density functional theory (DFT) investigation of the mechanisms of oxide growth at Al(100), Al(110) and Al(111) up to 1 monolayer (ML) coverage of O-atoms with 0.125 ML increments. We found that the surface binding site preferences of O-atoms are largely affected by the presence of neighboring O-atoms. Based on this we constructed two oxide growth models: the formation of clusters that evolve to stripes with increasing coverage and the formation of a more homogeneous distribution of O-atoms. While the former model is characterized by a lower symmetry of distribution of O-atoms at the surfaces, the latter corresponds to higher symmetries. We found that the prevalence of each oxide growth mode depends on the coverage of O-atoms and that this dependency is different for each surface. For Al(100) and Al(110), up to coverages of 1 ML the oxide grows preferably via the formation of clusters that evolve to stripes with increasing coverage, while for Al(111) the stripes and clusters are the preferred growth mode for coverages up to 0.375 ML, beyond which the homogeneous growth mode is energetically favored. The calculated Al-O pair distribution functions show that the formation of clusters and stripes leads to shorter Al-O bond lengths when compared to the homogeneous growth. The oxides formed at Al(100) and Al(110) have Al-O bond lengths and geometries typical of the shorter bonds of -alumina while at Al(111) the bond lengths are typical of -alumina and -alumina. These results suggest that for low coverages, the oxides formed at Al(100) and Al(110) are resemblant of defective -alumina while the oxide formed at Al(111) is similar to less disordered -alumina and -alumina. For Al(111), the small energy difference between the growth of clusters and stripes and homogeneous growth does not exclude the coexistence of both growth modes; this could lead to the formation of a defective or amorphous oxide.

  • 80.
    Lousada, Claudio M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Oxygen adsorption onto pure and doped Al surfaces - the role of surface dopants2015Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, nr 3, s. 1667-1679Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using density functional theory (DFT) with the PBE0 density functional we investigated the role of surface dopants in the molecular and dissociative adsorption of O-2 onto Al clusters of types Al-50, Al50Alad, Al50X and Al49X, where X represents a dopant atom of the following elements Si, Mg, Cu, Sc, Zr, and Ti. Each dopant atom was placed on the Al(111) surface as an adatom or as a substitutional atom, in the last case replacing a surface Al atom. We found that for the same dopant geometry, the closer is the ionization energy of the dopant element to that of elemental Al, the more exothermic is the dissociative adsorption of O-2 and the stronger are the bonds between the resulting O atoms and the surface. Additionally we show that the Mulliken concept of electronegativity can be applied in the prediction of the dissociative adsorption energy of O-2 on the doped surfaces. The Mulliken modified second-stage electronegativity of the dopant atom is proportional to the exothermicity of the dissociative adsorption of O-2. For the same dopant element in an adatom position the dissociation of O-2 is more exothermic when compared to the case where the dopant occupies a substitutional position. These observations are discussed in view of the overlap population densities of states (OPDOS) computed as the overlap between the electronic states of the adsorbate O atoms and the clusters. It is shown that a more covalent character in the bonding between the Al surface and the dopant atom causes a more exothermic dissociation of O-2 and stronger bonding with the O atoms when compared to a more ionic character in the bonding between the dopant and the Al surface. The extent of the adsorption site reconstruction is dopant atom dependent and is an important parameter for determining the mode of adsorption, adsorption energy and electronic structure of the product of O-2 adsorption. The PBE0 functional could predict the existence of the O-2 molecular adsorption product for many of the cases investigated here.

  • 81.
    Lousada, Claudio M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Surface Chemistry of Oxygen on Aluminum-Performance of the Density Functionals: PBE, PBE0, M06, and M06-L2016Ingår i: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 37, nr 9, s. 787-794Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated the performance of the density functional theory (DFT) functionals PBE, PBE0, M06, and M06-L for describing the molecular and dissociative adsorption of O2 onto pure and doped Al(111) surfaces. Adsorption of O2 was studied at the perfect Al(111) surface and compared with the case where an additional Al atom was present as an adatom. Additionally, we studied how these functionals perform when different dopants are present at the Al(111) surface in two distinct geometries: as an adatom or as a substitutional atom replacing an Al atom. The performance of the different functionals is greatly affected by the surface geometry. The inclusion of Hartree-Fock exchange in the functional leads to slight differences in adsorption energies for molecular adsorption of O2. These differences become very pronounced for dissociative adsorption, with the hybrids PBE0 and M06 predicting more exergonic adsorption than PBE and M06-L. Furthermore, PBE0 and M06 predicted trends in adsorption energies for defective and perfect surfaces which are in line with the experimental knowledge of the effects of surface defects in adsorption energies. The predictions of the non-hybrids PBE and M06-L point in the opposite direction. The analysis of the contributions of the van der Waals (vdW) forces to the adsorption energies reveals that the PBE and PBE0 functionals have similar difficulties in describing vdW interactions for molecular adsorption of O2 while the M06 functional can give a description of these forces with an accuracy which is at least similar to that of the correction of the D3 type.

  • 82.
    Lousada, Claudio Miguel
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Johansson, Adam Johannes
    Korzhavyi, Pavel A
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Thermodynamics of H2O Splitting and H-2 Formation at the Cu(110)-Water Interface2015Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 25, s. 14102-14113Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We used density functional theory to investigate the sequential oxidation of the (110) surface of fcc copper triggered by the dehydrogenation of molecularly adsorbed water the reactions studied did not involve any oxygen besides that present in the water molecules. According to the obtained Gibbs free energies, the formation of half a inonolayer of HO and the corresponding amount of hydrogen gas is spontaneous (Delta(r)G(0) < 0) starting from a monolayer of adsorbed water at Cu(110) The subsequent dehydrogenation steps necessary to ultimately form one monolayer of O atoms are nonspontaneous (Delta(r)G(o) > 0). We present a computationally efficient approach which shows good accuracy for determining the solvation energy of the Cu(110) surface, deviating only by 0.014 eV from literature data. The solvation effect imparts additional stabilization to several oxygen-containing species adsorbed at the Cu(110) surface. Additionally, we investigated the effect of an overlayer of water molecules at the surface where the dehydrogenation of H2O takes place. We found that even though the Gibbs free energy changes associated with the first steps of dehydrogenation of H2O at the Cu surface do not differ substantially from those without an additional water layer, subsequent dehydrogenation steps are favored by as much as 1.6 eV. In view of these results we discuss the importance of the hydrogen-bonding network formed when an overlayer of H2O is present in determining the reactivity of surface species. Additionally, we found a considerable effect of the second water layer on the surface relaxation, which differs significantly from the case where no second water layer is present. The hydrogen-bonding network has an important role in affecting the chemistry of the surface species but also in stabilizing the surface itself, which in turn affects the surface relaxation. These findings shed additional light on the modeling of surface processes in solution, which have implications for corrosion science and catalysis.

  • 83.
    Lousada, Claudio Miguel
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Soroka, Inna L.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Yagodzinskyy, Y.
    Tarakina, N. V.
    Todoshchenko, O.
    Hänninen, H.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Gamma radiation induces hydrogen absorption by copper in water2016Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, artikel-id 24234Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One of the most intricate issues of nuclear power is the long-term safety of repositories for radioactive waste. These repositories can have an impact on future generations for a period of time orders of magnitude longer than any known civilization. Several countries have considered copper as an outer corrosion barrier for canisters containing spent nuclear fuel. Among the many processes that must be considered in the safety assessments, radiation induced processes constitute a key-component. Here we show that copper metal immersed in water uptakes considerable amounts of hydrogen when exposed to γ-radiation. Additionally we show that the amount of hydrogen absorbed by copper depends on the total dose of radiation. At a dose of 69 kGy the uptake of hydrogen by metallic copper is 7 orders of magnitude higher than when the absorption is driven by H2(g) at a pressure of 1 atm in a non-irradiated dry system. Moreover, irradiation of copper in water causes corrosion of the metal and the formation of a variety of surface cavities, nanoparticle deposits, and islands of needle-shaped crystals. Hence, radiation enhanced uptake of hydrogen by spent nuclear fuel encapsulating materials should be taken into account in the safety assessments of nuclear waste repositories.

  • 84. Petrik, M. V.
    et al.
    Gornostyrev, Y. N.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Point defect interactions with Guinier-Preston zones in Al-Cu based alloys: Vacancy mediated GPZ to θ′-phase transformation2019Ingår i: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 165, s. 123-127Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The energetics of point defect interactions with a Guinier-Preston zone (GPZ) in Al alloys are systematically studied using ab initio calculations and a supercell approach. We find that vacancies can be trapped by GPZs and that the presence of a vacancy in a Cu layer qualitatively changes the solute–GPZ interactions. A vacancy mediated mechanism of GPZ to θ′-phase transformation is suggested and shown to be thermodynamically feasible, which involves the formation of structural vacancies and splitting of a GPZ layer into two half-vacant Cu layers. This mechanism, in combination with the calculated attractive solute-vacancy interactions, is predicted to result in the solute segregation at the interface between Al matrix and the forming θ′-phase precipitate.

  • 85.
    Razumovskiy, Vsevolod I.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Isaev, E. I.
    Ruban, Andrei V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Ab initio calculations of elastic properties of Pt-Sc alloys2008Ingår i: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 16, nr 8, s. 982-986Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Elastic properties of substitutionally disordered Pt-rich Pt-Sc alloys and L1(2)-ordered Pt3Sc compound are derived from the first-principles calculations based on the exact muffin-tin orbitals (EMTO) method. We demonstrate that these alloys should exhibit a ductile behavior, which combined with relatively high melting temperature and strong cohesive properties make them a very promising candidate for high-temperature applications.

  • 86.
    Razumovskiy, Vsevolod I.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Isaev, Eyvaz I.
    Ruban, Andrei V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    New Pt-Based Superalloy System Designed from First Principles2009Ingår i: Advanced Intermetallic-Based Alloys For Extreme Environment And Energy Applications / [ed] Palm M; Bewlay BP; He YH; Takeyama M; Wiezorek JMK, 2009, Vol. 1128, s. 233-238Konferensbidrag (Refereegranskat)
    Abstract [en]

    Pt-Sc alloys with the gamma-gamma' microstructure are proposed as a basis for a new generation of Pt-based superalloys for ultrahigh-temperature applications. This alloy system was identified on the basis of first-principles calculations. Here we discuss the prospects of the Pt-Sc alloy system on the basis of calculated elastic properties, phonon spectra, and defect formation energies.

  • 87.
    Razumovskiy, Vsevolod I.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Ruban, Andrei V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Ab-initio calculations of kinetic properties in ZrC and TiC carbides2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Self-diffusion of the metal and carbon atoms in TiC and ZrC carbides is studied by first principles methods. Our calculations yield point defects energies, vacancy jump barriers and diffusion pre-factors in TiC and ZrC. The results are in reasonable agreement with the available experimental data and suggest that the self-diffusion mechanism for metal atoms in these carbides may involve nearest-neighbor vacancy pairs (one metal and one carbon vacancy).

  • 88.
    Razumovskiy, Vsevolod I.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Ruban, Andrei V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Effect of temperature on the elastic anisotropy of pure Fe and Fe0.9Cr0.1 random alloy2011Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 107, nr 20, artikel-id 205504Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The elastic properties of pure iron and substitutionally disordered 10 at. % Cr Fe-Cr alloy areinvestigated as a function of temperature using first-principles electronic-structure calculations bythe exact muffin-tin orbitals method. The temperature effects on the elastic properties are includedvia the electronic, magnetic, and lattice expansion contributions. We show that the degree ofmagnetic order in both pure iron and Fe90Cr10 alloy mainly determines the dramatic change of theelastic anisotropy of these materials at elevated temperatures. The effect of lattice expansion isfound to be secondary but also very important for quantitative modeling.

  • 89.
    Razumovskiy, Vsevolod I.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Ruban, Andrei V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    First-principles study of elastic properties of Cr- and Fe-rich Fe-Cr alloys2011Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, nr 2, artikel-id 024106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Elastic properties of substitutionally disordered Cr- and Fe-rich Fe-Cr alloys are derived from first-principles calculations using the exact muffin-tin orbitals method and the coherent potential approximation. A peculiarity in the concentration dependence of elastic constants in Fe-rich alloys is demonstrated and related to a change in the Fermi surface topology. Our calculations predict high values for the elastic constants of Cr-rich Fe-Cr alloys, but at the same time show that these alloys could be rather brittle according to the Pugh criterion (the ratio between shear and bulk moduli is calculated to be greater than 0.5).

  • 90.
    Razumovskiy, Vsevolod I.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Ruban, Andrei V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Odqvist, Joakim
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Vacancy-cluster mechanism of metal-atom diffusion in substoichiometric carbides2013Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, nr 5, s. 054203-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We find, using ab initio atomistic simulations of vacancy-mediated diffusion processes in TiC and ZrC, that a multivacancy self-diffusion mechanism is operative for metal-atom diffusion in substoichiometric carbides. It involves a special type of a stable point defect, a metal vacancy "dressed" in a shell of carbon vacancies. We show that this vacancy cluster is strongly bound and can propagate through the lattice without dissociating.

  • 91.
    Razumovskiy, Vsevolod
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Flerskalig materialmodellering. Mat Ctr Leoben Forsch GmbH, A-8700 Leoben, Austria.
    Ruban, Andrei
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Flerskalig materialmodellering.
    Odqvist, Joakim
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Dilner, David
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    Korzhavyi, Pavel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Effect of carbon vacancies on thermodynamic properties of TiC-ZrC mixed carbides2014Ingår i: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 46, s. 87-91Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermodynamic properties of a TiZrC mixed carbide system are investigated by first-principles methods within density functional theory. Carbon vacancies are found to have a significant contribution to the thermodynamics of TiZrC mixed carbides. The temperature effect on the thermodynamic properties of the system is calculated taking into consideration the corresponding electronic and vibrational thermal excitations.

  • 92.
    Ruban, Andrei V.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    First-principles theory of magnetically driven anomalous ordering in bcc Fe-Cr alloys2008Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, nr 9, s. 094436-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ab initio perturbation-theory techniques, such as the generalized perturbation method and magnetic force theorem, are used to determine the Heisenberg exchange interaction parameters and the effective cluster interactions in Fe-rich bcc Fe-Cr alloys in different magnetic states. We establish a direct connection between chemical and magnetic exchange interactions, as well as their dependence on the global magnetic state of the alloy. These findings have important implications for phase equilibria in magnetic alloys. In particular, we demonstrate that the experimentally reported concentration interval of anomalous ordering in Fe-Cr alloys is determined by the thermal history of the alloys through the value of global magnetization at the annealing temperature.

  • 93.
    Ruban, Andrei V.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Simak, S. I.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Theoretical investigation of bulk ordering and surface segregation in Ag-Pd and other isoelectornic alloys2007Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, nr 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bulk ordering in Ag-Pd and other isoelectronic alloys is investigated theoretically by a number of first-principles techniques. The electronic structure and total energy have been calculated by the Green's function Korringa-Kohn-Rostocker and full-potential plane wave methods. The effective cluster interactions of the Ising-type Hamiltonian have been obtained by the screened generalized perturbation method. They reveal a complex concentration-dependent ordering behavior in these alloys due to band filling and Fermi surface effects. In particular we show that long-period superstructures are gradually stabilized by a great number of relatively weak long-range effective pair- and three-site interactions, which can be seen as collective effect. A similar complex concentration dependence is also found for surfaces of Ag-Pd alloys. The surface composition of the (111) and (100) surface of Ag75Pd25, Ag50Pd50, and Ag33Pd67 alloys have been then investigated by the surface Green's function technique and the screened generalized perturbation method for the effective interactions of the Ising-type Hamiltonian and the grand canonical Monte Carlo method for statistical thermodynamic simulations at finite temperatures. We compare our results with experimental data and other theoretical calculations.

  • 94. Ruban, Andrei V.
    et al.
    Simak, S. I.
    Korzhavyi, Pavel A.
    KTH, Tidigare Institutioner, Materialvetenskap.
    Skriver, H. L.
    Screened Coulomb interactions in metallic alloys. II. Screening beyond the single-site and atomic-sphere approximations2002Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 66, nr 2Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A quantitative description of the configurational part of the total energy of metallic alloys with substantial atomic size difference cannot be achieved in the atomic-sphere approximation: It needs to be corrected at least for the multipole-moment interactions in the Madelung part of the one-electron potential and energy. In the case of a random alloy such interactions can be accounted for only by lifting the atomic-sphere and single-site approximations, in order to include the polarization due to local environment effects. Nevertheless, a simple parametrization of the screened Coulomb interactions for the ordinary single-site methods, including the generalized perturbation method, is still possible. We obtained such a parametrization for bulk and surface NiPt alloys, which allows one to obtain quantitatively accurate effective interactions in this system.

  • 95.
    Sandberg, Nils
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik. Swedish Radiat Safety Author, Sweden.
    Chang, Z.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Messina, Luca
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Olsson, Pär
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Korzhavyi, Pavel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Modeling of the magnetic free energy of self-diffusion in bcc Fe2015Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, nr 18, artikel-id 184102Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A first-principles based approach to calculating self-diffusion rates in bcc Fe is discussed with particular focus on the magnetic free energy associated with diffusion activation. First, the enthalpies and entropies of vacancy formation and migration in ferromagnetic bcc Fe are calculated from standard density functional theory methods in combination with transition state theory. Next, the shift in diffusion activation energy when going from the ferromagnetic to the paramagnetic state is estimated by averaging over random spin states. Classical and quantum mechanical Monte Carlo simulations within the Heisenberg model are used to study the effect of spin disordering on the vacancy formation and migration free energy. Finally, a quasiempirical model of the magnetic contribution to the diffusion activation free energy is applied in order to connect the current first-principles results to experimental data. The importance of the zero-point magnon energy in modeling of diffusion in bcc Fe is stressed.

  • 96.
    Sandberg, Nils
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Chang, Zhongwen
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Olsson, Pär
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Korzhavyi, Pavel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Modeling of the magnetic free energy of self-diusion in bcc FeManuskript (preprint) (Övrigt vetenskapligt)
  • 97.
    Sandberg, Nils
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Korzhavyi, Pavel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Theoretical study of irradiation induced hardening and embrittlement in spent nuclear fuel holders, relevant for the Swedish long-term storage2009Rapport (Refereegranskat)
  • 98.
    Sandström, Rolf
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Korzhavyi, Pavel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Use of elastic constants based on ab initio computation in materials optimisation of austenitic stainless steels2014Ingår i: Canadian metallurgical quarterly, ISSN 0008-4433, E-ISSN 1879-1395, Vol. 53, nr 3, s. 282-291Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of ab initio quantum mechanics methods to compute elastic constants of austenitic stainless steels is reviewed. It is demonstrated that the elastic constants can be predicted accurately as a function of composition. This enables the use of materials optimisation techniques to develop new materials that are systematically adapted to specific components. After the design criteria and the target function to be optimised have been formulated, the optimum property combination can be searched for. The properties involved constitute a property space, where domains with active design criteria are identified. In the present paper, the domain where the stiffness is the controlling property is considered. Cost, weight and environmental impact minimisation is analysed. It turns out that for all three target functions, austenitic stainless steels with low chromium and nickel contents are preferred materials.

  • 99. Schmitz, G. J.
    et al.
    Engström, A.
    Bernhardt, R.
    Prahl, U.
    Adam, L.
    Seyfarth, J.
    Apel, M.
    Agelet De Saracibar, C.
    Korzhavyi, Pavel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Ågren, John
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Patzak, B.
    Software Solutions for ICME2016Ingår i: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 68, nr 1, s. 70-76Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Integrated Computational Materials Engineering expert group (ICMEg), a coordination activity of the European Commission, aims at developing a global and open standard for information exchange between the heterogeneous varieties of numerous simulation tools. The ICMEg consortium coordinates respective developments by a strategy of networking stakeholders in the first International Workshop on Software Solutions for ICME, compiling identified and relevant software tools into the Handbook of Software Solutions for ICME, discussing strategies for interoperability between different software tools during a second (planned) international workshop, and eventually proposing a scheme for standardized information exchange in a future book or document. The present article summarizes these respective actions to provide the ICME community with some additional insights and resources from which to help move this field forward.

  • 100. Shmakov, I. G.
    et al.
    Razumov, I. K.
    Gorbatov, O. I.
    Gornostyrev, Yu. N.
    Korzhavyi, Pavel
    KTH, Skolan för industriell teknik och management (ITM).
    Decomposition kinetics in Fe-Cu dilute alloys. Monte Carlo simulation using concentration-dependent interactions2016Ingår i: JETP Letters: Journal of Experimental And Theoretical Physics Letters, ISSN 0021-3640, E-ISSN 1090-6487, Vol. 103, nr 2, s. 112-116Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A generalization of the statistical (Monte Carlo) simulation technique for determining the structure of alloys is proposed. It takes into account the dependence of effective interactions between the atoms of a dissolved chemical element on their local concentration. Using the ab initio parametrization of the model, the decomposition of the bcc Fe-Cu alloy accompanied by the formation of Cu nanoprecipitates is studied. It is shown that the concentration dependence of effective interactions significantly affects the decomposition kinetics by displacing its onset to longer times in agreement with the experiment.

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