First-principles study of (Ti 5−xMg x)Si 3 phases with the hexagonal D8 8 structure: Elastic properties and electronic structure

Abstract

Structural stability, elastic and electronic properties of (Ti 5− x Mg x )Si 3 with D8 8 structure have been investigated by first-principles calculations. The obtained formation enthalpies demonstrated that the structure stability of (Ti 5− x Mg x )Si 3 was eventually lowered with increasing x. Then the independent elastic constants of (Ti 5− x Mg x )Si 3 were calculated, and the obtained results indicated that (Ti 2Mg 3)Si 3 and Mg 5Si 3 were mechanically instable. With Voigt–Reuss–Hill approximation, the calculated elastic modulus B, G and E of (Ti 5− x Mg x )Si 3 were reduced with increasing x, whereas the ductility was somewhat improved. The elastic anisotropy of (Ti 5− x Mg x )Si 3 was also studied in details. Furthermore, the electronic density of states and charge density distribution were investigated to reveal the inherent mechanism for stability and elastic properties of (Ti 5− x Mg x )Si 3 phases.