First-principles study of (Ti5−xMgx)Si3 phases with the hexagonal D88 structure: Elastic properties and electronic structure

Structural stability, elastic and electronic properties of (Ti5−xMgx)Si3 with D88 structure have been investigated by first-principles calculations. The obtained formation enthalpies demonstrated that the structure stability of (Ti5−xMgx)Si3 was eventually lowered with increasing x. Then the independent elastic constants of (Ti5−xMgx)Si3 were calculated, and the obtained results indicated that (Ti2Mg3)Si3 and Mg5Si3 were mechanically instable. With Voigt–Reuss–Hill approximation, the calculated elastic modulus B, G and E of (Ti5−xMgx)Si3 were reduced with increasing x, whereas the ductility was somewhat improved. The elastic anisotropy of (Ti5−xMgx)Si3 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 (Ti5−xMgx)Si3 phases.