High‐Pressure Effect on Elastic Constants and Their Related Properties of MgCa Intermetallic Compound

Abstract

Structural parameters, elastic constants, and their related properties of MgCa with a cubic CsCl‐type structure under high pressure up to 16 GPa are investigated using the pseudopotential plane‐wave approach in the framework of the density functional theory as implemented in the CASTEP code. The results indicate that MgCa possesses a brittle nature below 1.4 GPa and begins to be prone to ductility when the pressure goes beyond this value. The tetragonal shear parameter is found to vanish at around 7 GPa. The analyses of the anisotropy factors show that MgCa is highly anisotropic. The magnitude of the anisotropy increases monotonically with applied pressure. The single crystal azimuthal anisotropy for longitudinal and transverse waves is determined. The variation of the longitudinal and shear‐wave velocities with the direction of propagation is estimated at 0 and 16 GPa pressure. The Cauchy condition is found to be strongly violated, reflecting the important contribution from the noncentral many‐body forces in the crystal. In addition, the specific heat capacity CV and the entropy S at elevated temperatures up to 600 K are studied. At zero‐pressure and T = 300 K, our calculation yields values of CV ≈ 47.31 J mol−1 K−1 and S ≈ 66.06 J mol−1 K−1.