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Title: Anharmonicity, mechanical instability, and thermodynamic properties of the Cr-Re σ-phase

Using density-functional theory in combination with the direct force method and molecular dynamics we investigate the vibrational properties of a binary Cr-Re σ-phase. In the harmonic approximation, we have computed phonon dispersion curves and density of states, evidencing structural and chemical effects. We found that the σ-phase is mechanically unstable in some configurations, for example, when all crystallographic sites are occupied by Re atoms. By using a molecular-dynamics-based method, we have analysed the anharmonicity in the system and found negligible effects (∼0.5 kJ/mol) on the Helmholtz energy of the binary Cr-Re σ-phase up to 2000 K (∼0.8T{sub m}). Finally, we show that the vibrational contribution has significant consequences on the disordering of the σ-phase at high temperature.
Authors:
;  [1] ;  [2] ;  [3]
  1. ICAMS, Ruhr University Bochum, Universität Str. 150, D-44801 Bochum (Germany)
  2. SIMAP, UMR CNRS-INPG-UJF 5266, BP 75, F-38402 Saint Martin d’Hères (France)
  3. Department of Earth Sciences, Department of Physics and Astronomy, London Centre for Nanotechnology and Thomas Young Centre-UCL, University College London, Gower Street, London WC1E 6BT (United Kingdom)
Publication Date:
OSTI Identifier:
22253294
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 14; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; APPROXIMATIONS; CRYSTALLOGRAPHY; DENSITY; DENSITY FUNCTIONAL METHOD; DISPERSIONS; INSTABILITY; MOLECULAR DYNAMICS METHOD; TEMPERATURE RANGE 0400-1000 K; THERMODYNAMIC PROPERTIES