First-principles study on structural, elastic and thermodynamic properties of ZrxNb1-x alloys under high pressure

Zr-Nb alloys have attracted the interest of physicists due to their excellent high-temperature resistance and corrosion resistance as a binary alloy. However, there are seldom studies on the overall system of binary Zr-Nb alloys, in particular, the different doping ratios of Zr-Nb elements under high pressure. Here, the mechanical and thermodynamic properties of ZrxNb(1-x) alloys at high pressure are systematically studied and compared by using the plane wave pseudopotential within density functional theory. By analyzing the elastic parameters, we find that ZrxNb(1-x) alloys (x = 0.1, 0.2, 0.3, and 0.33) may have a phase-change-precursor in the pressure range of 30-70 GPa. This situation is delayed with the increase of the Zr content, indicating that the increase in Zr content can improve the mechanical stability of the ZrxNb(1-x) alloys. The value of B/G is significantly greater than 1.75, suggesting that ZrxNb(1-x) alloys generally have ductility within 90 GPa. Moreover, we also find a higher Zr content and higher pressure environment will enhance the anisotropy of ZrxNb(1_x) alloys according to the law of anisotropy index change. Simultaneously, we calculated the thermodynamic expansion coefficient & alpha; and found that it decreased with the increase of the pressure, and decreased as the temperature decreased. Surprisingly, when pressure exceeds 50 GPa, the expansion coefficient of ZrxNb(1-x) alloys shows a trend of slightly linear reduction, indicating that the thermal stability under high pressure will become better. In other words, the application of ZrxNb(1-x) alloy under high pressure might be achieved. Our research results may provide a certain reference for the elastic and thermodynamic properties of ZrxNb(1_x) alloy under high pressure in the future.