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 (∼0.8Tm). Finally, we show that the vibrational contribution has significant consequences on the disordering of the σ-phase at high temperature.
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14 April 2014
Research Article|
April 08 2014
Anharmonicity, mechanical instability, and thermodynamic properties of the Cr-Re σ-phase
Mauro Palumbo;
Mauro Palumbo
a)
1ICAMS,
Ruhr University Bochum
, Universität Str. 150, D-44801 Bochum, Germany
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Suzana G. Fries;
Suzana G. Fries
1ICAMS,
Ruhr University Bochum
, Universität Str. 150, D-44801 Bochum, Germany
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Alain Pasturel;
Alain Pasturel
2
SIMAP
, UMR CNRS-INPG-UJF 5266, BP 75, F-38402 Saint Martin d’Hères, France
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Dario Alfè
Dario Alfè
3Department 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
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J. Chem. Phys. 140, 144502 (2014)
Article history
Received:
October 21 2013
Accepted:
March 18 2014
Citation
Mauro Palumbo, Suzana G. Fries, Alain Pasturel, Dario Alfè; Anharmonicity, mechanical instability, and thermodynamic properties of the Cr-Re σ-phase. J. Chem. Phys. 14 April 2014; 140 (14): 144502. https://doi.org/10.1063/1.4869800
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