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  • 1.
    Ericsson, A.
    et al.
    Division of Solid Mechanics, Lund University, PO Box 118, Lund, SE 22100, Sweden.
    Fisk, Martin
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Division of Solid Mechanics, Lund University, PO Box 118, Lund, 22100, SE, Sweden.
    Hallberg, H.
    Division of Solid Mechanics, Lund University, PO Box 118, Lund, SE 22100, Sweden.
    Modeling of nucleation and growth in glass-forming alloys using a combination of classical and phase-field theory2019In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 165, p. 167-179Article in journal (Refereed)
    Abstract [en]

    For metallic glasses, it is of vital importance to understand the glass formation properties and to be able to predict the crystallization process in the supercooled liquid. In the present work, we model the process of nucleation and growth using a combination of classical nucleation and phase-field theory. A diffusion coupled phase-field model is used to evaluate the work of formation and the growth behavior of the critical nucleus. The results are combined with classical nucleation and JMAK theory in order to estimate the glass forming ability of the compositions Cu64Zr36, Cu10Zr7 and CuZr2 in terms of TTT-diagrams and critical cooling rates. It is found that the work of formation of the critical nucleus from the phase-field theory agrees with the classical theory when the critical size is larger than the width of the solid-liquid interface. At smaller critical sizes, the work of formation deviates approximately linearly between the two theories. Furthermore, it is shown that the growth behavior from the phase-field simulations agree with analytical expressions of the growth rate from the classical theory.

  • 2.
    Fisk, Martin
    et al.
    Malmö högskola, School of Technology (TS).
    Ion, John C.
    Lindgren, Lars-Erik
    Flow stress model for IN718 accounting for evolution of strengthening precipitates during thermal treatment2014In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 82, no 1, p. 531-539Article in journal (Refereed)
    Abstract [en]

    A flow stress model describing precipitate hardening in the nickel based alloy InconelÒ 718 following thermal treatment is presented. The interactions between precipitates and dislocations are included in a dislocation density based material model. Compression tests have been performed using solution annealed, fully-aged and half-aged material. Models were calibrated using data for solution annealed and fully-aged material, and validated using data from half-aged material. Agreement between experimental data and model predictions is good.

  • 3.
    Hiremath, Praveenkumar
    et al.
    Division of Mechanics, Lund University.
    Melin, Solveig
    Division of Mechanics, Lund University.
    Bitzek, Erik
    Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany ; Computational Materials Design, Düsseldorf, Germany.
    Olsson, Pär A T
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Division of Mechanics, Lund University.
    Effects of interatomic potential on fracture behaviour in single- and bicrystalline tungsten2022In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 207, p. 1-18, article id 111283Article in journal (Refereed)
    Abstract [en]

    In the present work, we have evaluated the performance of different embedded atom method (EAM) andsecond-nearest neighbour modified embedded atom method (2NN-MEAM) potentials based on their predictive capabilities for modelling fracture in single- and bicrystalline tungsten. As part of the study, a new 2NN-MEAM was fitted with emphasis on reproducing surface, unstable stacking fault and twinning energies as derived fromdensity functional theory (DFT) modelling. The investigation showed a systematic underestimation of surfaceenergies by most EAM potentials, and a significant variation in unstable stacking and twinning fault energies.Moreover, the EAM potentials in general lack the ability to reproduce the DFT traction–separation (TS) curves. The shorter interaction length and higher peak stress of the EAM TS curves compared to the 2NN-MEAM and DFT TS curves result in one order of magnitude higher lattice trapping than for cracks studied with 2NN-MEAM. These differences in lattice trapping can lead to significant qualitative differences in the fracture behaviour. Overall, the new 2NN-MEAM potential best reproduced fracture-relevant material properties and its results were consistent with fracture experiments. Finally, the results of fracture simulations were compared with analytical predictions based on Griffith and Rice theories, for which emerging discrepancies were discussed.

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  • 4.
    Hiremath, Praveenkumar
    et al.
    Division of Mechanics, Materials & Component Design, Lund University.
    Melin, Solveig
    Division of Mechanics, Materials & Component Design, Lund University.
    Olsson, Pär A T
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Phosphorus driven embrittlement and atomistic crack behavior in tungsten grain boundaries2024In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 244, p. 1-12, article id 113194Article in journal (Refereed)
    Abstract [en]

    We investigated the role of phosphorus (P) impurities on the fracture toughness and underlying failure mechanisms by means of classical atomistic modeling for a set of ⟨110⟩ symmetric tilt tungsten grain boundaries (GBs). This entailed the utilization of a quasi-static mode I displacement-controlled setup with cohesive zone volume elements (CZVEs) to study failure mechanisms and evaluate the fracture toughness of the GB cracks. The fracture toughness was estimated using three approaches: computing (i) the individual and (ii) the average energy release rate of CZVEs along the fractured surfaces and using them as inputs for the Griffith model, and(iii) relating the fracture toughness to crack propagation initiation. The cracks in all the pristine GBs evolved in a brittle fashion, occasionally forming facetted cleavage planes. Upon introduction of impurities, other mechanisms such as void formation and crack-tip transformation were also observed. Depending on the GBproximity of the occupied segregation sites, local strengthening was seen occasionally for individual CZVEs and at the crack-tip, which was triggered by local impurity-induced crack deflection onto planes with higher cohesion. But when the fracture toughness from the averaged energy release rate was considered, an overall reduction with increasing impurity segregation was found, although to a varying degree for different GBs. This indicates an overall increased degree of embrittlement with increasing P-segregation at the GBs, which concurs with most experimental results reported in the literature.

  • 5.
    Jernkvist, Lars Olof
    Malmö högskola, School of Technology (TS). Quantum Technologies AB, Uppsala Science Park, SE-75183 Uppsala, Sweden.
    Multi-field modelling of hydride forming metals Part II: application to fracture2014In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 85, p. 383-401Article in journal (Refereed)
    Abstract [en]

    In Part I of the present article, we formulated a continuum-based computational model for stress- and temperature-directed diffusion of hydrogen in metals that form brittle binary hydrides, such as Zr and Ti alloys. Among the space–time dependent parameters calculated by the model are the volume fraction and the mean orientation of hydride precipitates. These parameters are of importance for quantifying the embrittlement of hydrided materials. In this second part of the work, we use measured data for the strength and toughness of hydrided Zr alloys to correlate the local fracture properties of the two-phase (metal + hydride) material to the aforementioned parameters. The local fracture properties are used as space–time dependent input to a cohesive zone type submodel for fracture, which is fully integrated with the hydrogen transport model from Part I. The complete model is validated against fracture tests on hydrogen-charged Zr–2.5%Nb, a material used in nuclear reactor pressure tubes. More precisely, we study local embrittlement and crack initiation at a blunt and moderately stressed notch, resulting from gradual accumulation of hydrides at the notch during temperature cycling. We also simulate tests on crack initiation and growth by delayed hydride cracking, a subcritical crack growth mechanism with a complex temperature dependence. From the results of the simulations, we conclude that the model reproduces many observed features related to initiation and propagation of hydride induced cracks in the Zr–2.5%Nb material. In particular, it has the capacity to reproduce effects of the material’s temperature history on the fracture behaviour, which is important for many practical applications.

  • 6.
    Jernkvist, Lars Olof
    et al.
    Malmö högskola, Faculty of Technology and Society (TS).
    Massih, Ali
    Malmö högskola, Faculty of Technology and Society (TS).
    Multi-field modelling of hydride forming metals: part I: model formulation and validation2014In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 85, p. 363-382Article in journal (Refereed)
    Abstract [en]

    A computational model for hydrogen transport, hydrogen induced deformation and fracture in metals that form binary hydrides, such as Zr and Ti alloys, is presented. The model uses a continuum description of the two-phase (metal + hydride) material, and solves the multi-field partial differential equations for temperature and stress-directed hydrogen diffusion together with mechanical equilibrium in a three-dimensional finite element setting. Point-kinetics models are used for metal-hydride phase transformation and stress-directed orientation of hydride precipitates, while a cohesive zone fracture model caters for initiation and propagation of cracks. The local fracture properties of the hydrided material are correlated to the calculated local concentration and orientation of the hydride precipitates, which have a strong embrittling effect on the material. In Part I of this two-part paper, we present sub-models applied for the aforementioned phenomena together with a detailed description of their numerical implementation. The applicability of the model is then demonstrated by simulating five independent experiments on hydrogen transport, metal-hydride phase transformation and stress-directed hydride orientation in zirconium alloys. Based on the results, we conclude that the model captures these phenomena over a wide range of thermo-mechanical loading conditions, including thermal cycling. Part II of the paper is focussed on fracture, and includes details on the fracture model and its validation against tests and experiments on initiation and propagation of hydride induced cracks.

  • 7.
    Krause, Andreas M.
    et al.
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Olsson, Pär A T
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Lund University.
    Music, Denis
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Bjerkén, Christina
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Interstitial diffusion of hydrogen in M7C3 (M=Cr,Mn,Fe)2023In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 218, article id 111940Article in journal (Refereed)
    Abstract [en]

    To increase the understanding of the role of carbide precipitates on the hydrogen embrittlement of martensitic steels, we have performed a density functional theory study on the solution energies and energy barriers for hydrogen diffusion in orthorhombic M7C3 (M = Cr, Mn, Fe). Hydrogen can easily diffuse into the lattice and cause internal stresses or bond weakening, which may promote reduced ductility. Solution energies of hydrogen at different lattice positions have systematically been explored, and the lowest values are -0.28, 0.00, and 0.03 eV/H-atom for Cr7C3, Mn7C3, and Fe7C3, respectively. Energy barriers for the diffusion of hydrogen atoms have been probed with the nudged elastic band method, which shows comparably low barriers for transport via interstitial octahedral sites for all three systems. Analysis of the atomic volume reveals a correlation between low solution energies and energy barriers and atoms with large atomic volumes. Furthermore, it shows that the presence of carbon tends to increase the energy barrier. Our results can explain previous experimental findings of hydrogen located in the bulk of CrC precipitates and provide a solid basis for future design efforts of steels with high strength and commensurable ductility.

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  • 8.
    Massih, Ali
    et al.
    Malmö högskola, Faculty of Technology and Society (TS).
    Jernkvist, Lars Olof
    Malmö högskola, Faculty of Technology and Society (TS).
    Effect of additives on self-diffusion and creep of UO22015In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 110, p. 152-162Article in journal (Refereed)
    Abstract [en]

    The creep of UO2 doped with Nb2O5 and Cr2O3 has been assessed using a point defect model based on the law of mass action, and the diffusional creep according to the Nabarro-Herring mechanism, which relates the creep rate to the lattice self-diffusivity, the inverse of grain area and the applied stress. The self-diffusion coefficients of cation (U) and anion (O) are directly proportional to the concentrations of ions, which in turn are functions of dopant concentrations. The model has been used to evaluate past creep experiments on UO2 doped with Nb2O5 and Cr2O3 in concentrations up to about 1 mol%, with a varying grain size at different temperatures and applied stresses. The creep rate increases significantly with the dopant concentration and the putative model, after a modification of the creep rate coefficient, retrodict the measured data satisfactorily. A number of factors affecting creep rate and thereby our model computations are discussed.

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  • 9.
    Massih, Ali R
    et al.
    Malmö högskola, School of Technology (TS). Quantum Technologies, Uppsala Science Park, Uppsala SE-75183, Sweden.
    Jernkvist, Lars Olof
    Quantum Technologies, Uppsala Science Park, Uppsala SE-75183, Sweden.
    Nucleation and growth of second-phase precipitates under quenching and annealing2007In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 39, no 2, p. 349-358Article in journal (Refereed)
  • 10.
    Massih, Ali R
    et al.
    Malmö högskola, School of Technology (TS).
    Jernkvist, Lars Olof
    Stress orientation of second-phase in alloys: Hydrides in zirconium alloys2009In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 4, no 4, p. 1091-1097Article in journal (Refereed)
    Abstract [en]

    A model for precipitation of the plate-shaped second-phase under applied stress is presented. The precipitates in the matrix-precipitate system are represented by their local volume fraction and an orientation parameter that defines the alignment of a precipitate platelet in a given direction. Kinetic equations, based on diffusion theory and classical nucleation theory, are used to describe the time evolution of these two parameters. The model is used to describe the stress orientation of hydrides in Zr-alloys in light of experiments.

  • 11.
    Music, Denis
    et al.
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Chang, Keke
    Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, China.
    Selective oxidation of thermoelectric TiNiSn2021In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 198, article id 110682Article in journal (Refereed)
    Abstract [en]

    Multiscale modelling, involving thermodynamic assessment and molecular dynamics based on density functionaltheory, was employed to unravel oxidation mechanisms pertinent to half-Heusler TiNiSn (space group F-43m), inparticular counterintuitive Ni inertness. O2 molecules dissociate and chemisorb onto TiNiSn(001) and TiNiSn(110), which is followed by ingress of O. Both Ti and Sn egress, while Ni is less mobile. Such diffusion processesyield point defects (vacancies and interstitials) and give rise to Ti and Sn binary oxide formation, while Ni isinert, which may be corelated to its relatively low mobility. Based on the Mulliken analysis and thermodynamicsat 900 K, the Ti oxide formation sequence is suggested to be Ti2O3 → Ti3O5 → TiO2 → TiO. These data explain theexperimental observations on the Ni inertness during oxidation of TiNiSn.

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  • 12.
    Music, Denis
    et al.
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Malmö University, Biofilms Research Center for Biointerfaces.
    Khayyamifar, Sana
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Hektor, Johan
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Conflicting primary and secondary properties of thermoelectric devices – A case study on the thermomechanical behavior of ZrNiSn2023In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 230, article id 112530Article in journal (Refereed)
    Abstract [en]

    While the primary properties of thermoelectric devices, directly related to the conversion efficiency, are considered in design efforts, the secondary (thermomechanical) properties are often ignored or overlooked even though they can lead to failure. Here, thermomechanical properties of thermoelectric ZrNiSn in the amorphous and crystalline state (space group F-43m), comprising thermal conductivity, thermal expansion, elastic (Young’s) modulus, and thermal shock, are studied using density functional theory and two phonon models. Thermal conductivity is also a key primary property for thermoelectric applications. Amorphous ZrNiSn exhibits a fourfold lower thermal conductivity than the crystalline counterpart due to high phonon–phonon scattering, which is conducive to thermoelectric performance. However, this is conflicting since a high thermal conductivity value is required to attain high resistance to thermal shock. Due to stronger bonds in the crystalline counterpart, facilitated by the stronger Zr 3d – Ni 3d and Sn 5p – Ni 3d hybridization and higher coordination than in the amorphous state, the linear coefficient of thermal expansion is lower, and the elastic modulus is higher. Hence, the crystalline state yields higher resistance to thermal shock. It is suggested that samples entailing both amorphous and crystalline regions can concurrently satisfy the primary and secondary requirements for enhanced efficiency and durability.

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  • 13.
    Olsson, Pär
    Malmö högskola, Faculty of Technology and Society (TS).
    First principles investigation of the finite temperature dependence of the elastic constants of zirconium, magnesium and gold2015In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 99, p. 361-372Article in journal (Refereed)
    Abstract [en]

    The purpose of this work is to investigate how well the temperature dependence of the elastic constants of single crystal zirconium, magnesium and gold are reproduced by ab initio density functional theory (DFT). The modelling was conducted via the quasi-harmonic approximation with the exchange–correlation functional based on the local density approximation. For gold and magnesium, the low and high temperature dependency agrees well with measurements, whereas the transition between low and high temperature ranges occurs over a wider range of temperature than observed experimentally. For zirconium, the simulations qualitatively predict the temperature dependence of the isentropic elastic constants, where C12 and C13 increase with increasing temperature. Because this behaviour is absent for the isothermal elastic constants, the increase can be attributed to the transformation from isothermal to isentropic elastic constants.

  • 14.
    Olsson, Pär A T
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Division of Mechanics, Materials and Components, Lund University, Box 118, SE, Lund, 221 00, Sweden.
    Ab initio thermo-elasticity of δ-MHx (M=Zr, Ti)2023In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 218, article id 111953Article in journal (Refereed)
    Abstract [en]

    In the present work, we report the results of a systematic ab initio study of the thermo-elastic properties of -MH1.5 (M=Zr, Ti). This investigation serves three purposes: (i) Elucidate the fully anisotropic temperature dependent elastic constants of hydrides, (ii) address discrepancies in thermal expansion data reported in the literature and (iii) provide input data for thermodynamic-based phase-transformation modelling. Due to a reduced contribution from the vibrational free energy to the strain energy, in agreement with experimental observations we find that the temperature  dependent stiffness of hydrides vary to a much lesser degree than the matrix. For -ZrH1.5, we further find that Zener’s anisotropy ratio varies with temperature. Regarding the linear thermal expansion, our results indicate that it is highly temperature dependent. With the exception of a few outliers, our DFT data concurs well with experimental data, if the temperature range over which it was measured is taken into account.

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  • 15.
    Olsson, Pär A T
    et al.
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Division of Mechanics, Lund University, Box 118, Lund, SE-221 00, Sweden.
    Bergvall, Erik
    Tetra Pak Packaging Solutions AB, Ruben Rausings gata, Lund, SE-221 86, Sweden.
    Atomistic investigation of functionalized polyethylene-alumina interfacial strength and tensile behaviour2021In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 187, article id 110075Article in journal (Refereed)
    Abstract [en]

    We study the adhesion and tensile behaviour of bi-layer interfaces comprising polyethylene, doped with carbonyl and hydroxyl functional groups emanating from ozone treatment, and α" role="presentation">-Al2O3" role="presentation"> by means of density functional theory and classical atomistic modelling. The results show that the deformations are localized within the polymer and comprise chain slip, disentanglement and detachment from the substrate, where only the latter is notably affected by the doping. The binding energies and excess forces associated with the detachment of functional groups from the alumina substrate are of the order of 1.7 eV and 1 nN, respectively, for both types. Although such forces do not affect the maximum peak stress notably, they give rise to spikes in the traction-separation curves following the fibril formation and promote increased total work of fracture.

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  • 16.
    Olsson, Pär A T
    et al.
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Division of Mechanics, Materials and Components, Lund University.
    Hiremath, Praveenkumar
    Division of Mechanics, Materials and Components, Lund University.
    Melin, Solveig
    Division of Mechanics, Materials and Components, Lund University.
    Atomistic investigation of the impact of phosphorus impurities on the tungsten grain boundary decohesion2023In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 219, article id 112017Article in journal (Refereed)
    Abstract [en]

    In the present work, we have generated a new second-nearest neighbour modified embedded atom method potential (2NN-MEAM) for the W-P system to investigate the impact of P impurity segregation on the strength of symmetric [110] tilt coincident site lattice grain boundaries (GBs) in tungsten. By incorporating the impurity-induced reduction of the work of separation in the fitting strategy, we have produced a  potential that predicts decohesion behaviour as found by ab initio density functional theory (DFT) modelling. Analysis of the GB work of separation and generalized stacking fault energy data derived from DFT and the 2NN-MEAM potential show that P-impurities reduce the resistance to both cleavage and slip. Mode I tensile simulations reveal that the most dominant mode of GB failure is cleavage and that pristine GBs, which are initially ductile, on most accounts change to brittle upon introduction of impurities. Such tendencies are in line with experimentally observed correlations between P-impurity content and reduced ductility.   

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  • 17.
    Olsson, Pär
    et al.
    Malmö högskola, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Blomqvist, Jakob
    Malmö högskola, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Intergranular fracture of tungsten containing phosphorus impurities: A first principles investigation2017In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 139, p. 368-378Article in journal (Refereed)
    Abstract [en]

    In the present work we have studied the influence of phosphorus impurities on the grain boundary strength of tungsten by means of quantum mechanical calculations based on density functional theory. As model grain boundary we consider the high angle configuration. The results show that by the introduction of a clean (i.e. impurity free) grain boundary in the bulk, the strength and peak stress of the cohesive zone are reduced and they are further reduced by the introduction of impurities. This effect can be attributed to the formation of polar bonds between W and P, which leads to a weakening of the interface. Based on a thermodynamic analysis of the cohesive zone during the straining we find that diffusion of impurities may occur to retain thermodynamic equilibrium for constant chemical potential. This contributes to the gradual reduction of the peak stress related to fracture, which can contribute to diffusion driven delayed cracking, even when subjected to static loads.

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  • 18.
    Olsson, Pär
    et al.
    Malmö högskola, Faculty of Technology and Society (TS).
    Blomqvist, Jakob
    Malmö högskola, Faculty of Technology and Society (TS).
    Bjerkén, Christina
    Malmö högskola, Faculty of Technology and Society (TS).
    Massih, Ali
    Malmö högskola, Faculty of Technology and Society (TS).
    Ab initio thermodynamics investigation of titanium hydrides2015In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 97, p. 263-275Article in journal (Refereed)
    Abstract [en]

    We report the results of an ab initio -based density functional theory study of the thermodynamic and structural properties of titanium hydrides. The thermodynamic modelling contains contributions from both vibrational and electronic excitations to the free energy and is conducted using the quasi-harmonic approximation (QHA). The enthalpy, entropy and heat capacity are computed over a wide range of temperature (0≲T⩽1000 K) and found to concur well with available experimental data. The simulations show that the Debye temperature varies significantly with temperature below about 50 K demonstrating that the Debye model is too simplistic for thermodynamic modelling throughout the entire temperature spectrum. Comparing the Debye temperature from QHA with that calculated from low temperature elastic constants reveals limited agreement, which suggests that the actual frequency distribution characteristics do not comply with that of the Debye model. The calculated thermodynamic properties are found to show many similarities to those of zirconium hydrides, which are discussed.

  • 19.
    Olsson, Pär
    et al.
    Malmö högskola, School of Technology (TS).
    Massih, Ali
    Malmö högskola, School of Technology (TS).
    Blomqvist, Jakob
    Malmö högskola, School of Technology (TS).
    Alvarez Holston, Anna-Maria
    Bjerkén, Christina
    Malmö högskola, School of Technology (TS).
    Ab initio thermodynamics of zirconium hydrides and deuterides2014In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 86, p. 211-222Article in journal (Refereed)
    Abstract [en]

    We report the results of a systematic ab initio study of the elastic and thermodynamic properties of γ-ZrH, δ-View the MathML source-ZrD, and δ-ZrD1.5. In addition, pure α-Zr as well as the ε-ZrH2 and ε-ZrD2 phases are evaluated for reference. The calculations are performed using quantum mechanical density functional theory (DFT) with the frozen core projector augmented wave (PAW) approach and a generalised gradient approximated (GGA) exchange–correlation functional. To capture the variations of the thermodynamic quantities over a wide range of temperatures View the MathML source, the quasi-harmonic approximation approach is adopted where the influence of the vibrational and electronic free energies are included by means of the phonon and electron densities of state. This allows for quantifying the contributions of the electron density of states, which were not accounted for in the previous studies. All the pertinent elastic constants and phonon properties for the considered hydride/deuteride phases are calculated and compared with experimental data; which were not done before. We have further computed the entropy, heat capacity and enthalpy as well as low temperature thermodynamic properties such as the Debye temperature and the electronic heat capacity constant for all the hydride and deuteride phases. The results of our computations concur well with the corresponding data obtained by measurements that are reported in the literature and offer the necessary data and basis for multiscale modelling of zirconium alloys.

  • 20.
    Starikov, Sergei
    et al.
    Interdisciplinary Centre for Advanced Materials Simulation (ICAMS), Ruhr-Universität Bochum, 44801 Bochum, Germany.
    Grigorev, Petr
    Aix-Marseille Universite, CNRS, CINaM UMR 7325, Campus de Luminy, 13288 Marseille, France.
    Olsson, Pär A T
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Division of Mechanics, Materials and Components, Lund University, Box 118, SE-221 00, Lund, Sweden.
    Angular-dependent interatomic potential for large-scale atomistic simulation of W-Mo-Nb ternary alloys2024In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 233, article id 112734Article in journal (Refereed)
    Abstract [en]

    We present a new classical interatomic potential designed for simulation of the W-Mo-Nb system. The angular-dependent format of the potential allows for reproduction of many important properties of pure metals and complex concentrated alloys with good accuracy. Special attention during the development and validation of the potential was paid to the description of vacancies, screw dislocations and planar defects, as well as thermo-mechanical properties. Here, the applicability of the developed model is demonstrated by studying the temperature dependence of the elastic moduli and average atomic displacement in pure metals and concentrated alloys up to the melting point.

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