First-principles investigation into the effect of pressure on structural, electronic, elastic, elastic anisotropy, thermoelectric and thermodynamic properties of CaMgSi

Abstract

In this work, the structure, electronic, elastic, elastic anisotropy, thermoelectric, and thermodynamic properties of CaMgSi under pressure are calculated via first-principles methods. The optimized structure and lattice parameters are in agreement with previously published experimental results, indicating the methods used in this work are feasible and reliable. The calculated results show that the values of bulk modulus, B, Young’s modulus, E, and shear modulus, G, increase with the pressure overall, while the values of G and Y decrease in special pressure regimes from 20 to 24 GPa. Analyses of Poisson’s ratio, v, and Pugh’s modulus ratio, B/G, imply that CaMgSi is prone to change from brittle to ductile with increasing pressure. The transition from brittleness to ductility occurs at a pressure of 16 GPa. The value of Hv decreases with the pressure overall, although it increases over the pressure ranges of 16–20 GPa and 24–28 GPa. Universal elastic anisotropy increases at pressures from 4 to 24 GPa, while it decreases over the pressure ranges from 0–4 and from 24–28 GPa. Moreover, the variation of elastic anisotropy for G and E is larger compared to that of B. In addition, the electrical conductivity and electronic thermal conductivity decrease with increasing pressure based on the total density of states for CaMgSi. In addition, the heat capacity decreases with increasing pressure, indicating the reduction of lattice thermal conductivity, which is beneficial for thermoelectric performance, especially at pressures from 8 to 16 GPa. Meanwhile, the structural stability can be enhanced at higher pressures, while the thermal stability of crystalline CaMgSi becomes weaker with increasing pressure. The investigation presented in this work offers a comprehensive understanding of the effects of pressure on the mechanical, thermoelectric, and thermodynamic properties of CaMgSi, which can provide guidance for further theoretical work and practical applications.