Effects of pressure on anisotropic elastic properties and minimum thermal conductivity of D022-Ni3Nb phase: First-principles calculations

The elastic constants, formation enthalpies, elastic moduli, Poisson's ratios, acoustic velocities and Debye temperatures of D022-Ni3Nb phase at different pressures are determined using first-principles calculations. The effects of pressure on anisotropic elastic properties and minimum thermal conductivity are discussed in detail. It is found that the calculated equilibrium lattice parameters at 0 GPa well agree with the experimental results. The negative formation enthalpy indicates that Ni3Nb phase is thermodynamically stable in the ground state, and the stability becomes better as the pressure is increased. The bigger ratio of B/G (larger than 1.75) and positive Cauchy pressure indicate that Ni3Nb phase is ductile. Moreover, Ni3Nb phase exhibits high elastic anisotropy, and the elastic anisotropies become increasingly pronounced with the increase of pressure. Additionally, the anisotropic chemical bonds of Ni3Nb phase reduce the minimum thermal conductivity. The minimum thermal conductivity increases with the increased pressure.