Structural and mechanical properties of ternary MgCaSi phase: A study by density functional theory

Abstract

The structural, elastic, and electronic properties of multi-performance ternary phase MgCaSi have been investigated by density functional theory. The present results show that MgCaSi is thermodynamically and mechanically stable. The derived elastic constants indicate that the c axis is the easiest to compress, followed by the a and b axes. The bulk, shear, and Young’s moduli of MgCaSi are higher than these of the mother phase Ca2Si, demonstrating that the hardness of MgCaSi has been favorably improved. The higher Debye temperature of MgCaSi also indicates stronger interatomic interactions and better thermal conductivity. Although MgCaSi exhibits less brittleness based on Pugh’s empirical formula, Poisson’s ratio, and the Cauchy pressure, orthorhombic MgCaSi possesses lower anisotropy than Ca2Si based on several criteria. To reveal the bonding nature of MgCaSi, the electronic structures are further investigated. It is found that the strong Si−Si bond plays a significant role for structural stability and elastic properties.

First-Principles Thermoelectric Study of SrMgSi and CaMgGe Zintl-Phase Compounds

“…Moreover, Guo et al discovered a remarkably low thermal conductivity (0.56 W/m·K) in 1-1-1-type Zintl compound of NaCdSb, which is related to the fluctuation of bond length and strength in the Cd–Sb network. In addition to the abovementioned materials, alloys and Zintl compounds containing magnesium (Mg) have a wide range of applications in energy, aerospace, and other fields. , Recent studies have suggested Mg-containing TiNiSi-type compounds as a possible new family of TE materials due to the weak chemical bonds and the variety in constituent elements. − However, an in-depth understanding of the TE properties of this type of materials is far from complete. In particular, the TE properties of the ternary Zintl-phase SrMgSi and CaMgGe have not been explored, despite that both compounds were reported to have been synthesized …”