AB INITIO CALCULATIONS OF ELASTIC CONSTANTS OF BCC V-NB SYSTEM AT HIGH PRESSURES
First-principles total energy calculation based on the exact muffin-tin orbital and full potential linear muffin-tin orbital methods were used to calculate the equation of state and shear elastic constants of bcc V, Nb, and the V{sub 95}Nb{sub 05} disordered alloy as a function of pressure up to 6 Mbar. We found a mechanical instability in C{sub 44} and a corresponding softening in C at pressures {approx} 2 Mbar for V. Both shear elastic constants show softening at pressures {approx} 0.5 Mbar for Nb. Substitution of 5 at. % of V with Nb removes the instability of V with respect to trigonal distortions in the vicinity of 2 Mbar pressure, but still leaves the softening of C{sub 44} in this pressure region. We argue that the pressure induced shear instability (softening) of V (Nb) originates from the electronic system and can be explained by a combination of the Fermi surface nesting, electronic topological transition, and band Jahn-Teller effect.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 894332
- Report Number(s):
- UCRL-JRNL-211967; TRN: US0700140
- Journal Information:
- Journal of Physics and Chemistry of Solids, vol. 67, n/a, September 6, 2006, pp. 2056-2064, Journal Name: Journal of Physics and Chemistry of Solids, vol. 67, n/a, September 6, 2006, pp. 2056-2064
- Country of Publication:
- United States
- Language:
- English
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