Study of Structural, Elastic, and Mechanical Properties of LiNiPO₄ under Pressure by Ab-Initio Method

The structural, elastic, and mechanical properties of the LiNiPO₄ with an orthorhombic-type structure under pressure were investigated using first-principles calculations. The calculated structural parameters and elastic constants show a good agreement with the experimental and other theoretical values. The details of pressure dependences of the structural parameters and elastic constants are also presented and discussed. According to our calculation, we found that the deformation resistances along the axial direction are stronger than the deformation resistances in shape. It is also found, the elastic constant C₁₁ is always bigger than the C₃₃ at the same pressure, showing that it is easier to compress along the c-axis than along the a-axis. For the calculated results of the bulk modulus, shear modulus, and Young’s modulus with increasing pressure. The B/G ratio and the Poisson’s ratio show that the orthorhombic LiNiPO₄ behaves as a brittleness material at ambient pressure and has increment ductile under pressure.