Structural Stability, Thermodynamic and Elastic Properties of Cubic Zr0.5Nb0.5 Alloy under High Pressure and High Temperature

Structural stability, sound velocities, elasticity, and thermodynamic properties of cubic Zr0.5Nb0.5 alloy have been investigated at high pressure and high temperature by first-principles density functional calculations combined with the quasi-harmonic Debye model. A pronounced pressure-induced shear wave velocity stiffening in Zr0.5Nb0.5 alloy is observed at pressures above similar to 11 GPa, owing to its structural instability under high pressure, whose anomalous behavior is also observed in the end members of Zr-Nb alloys for Zr at similar to 13 GPa and for Nb at similar to 6 GPa upon compression, respectively. In addition, high-pressure elasticity and elastic-correlated properties of cubic Zr0.5Nb0.5 are reported, as compared with previous studies on Zr-Nb alloys with different compositions. A comprehensive study of the thermodynamic properties of cubic Zr0.5Nb0.5, such as heat capacity (C-v), thermal expansion coefficients (alpha), and Debye temperature (Theta(D)), are also predicted at pressures and temperatures up to 30 GPa and 1500 K using the quasi-harmonic Debye model.