Ab initio investigation on the phase stability of Ti ₃SiC ₂, Ti ₃Si _0.5Ge _0.5C ₂, and Ti ₃GeC ₂ at high pressures

Abstract

Phase stability of Ti ₃SiC ₂, Ti ₃Si _0.5Ge _0.5C ₂ and Ti ₃GeC ₂ under high hydrostatic pressures has been studied by ab initio calculations. The present results show that every phase undergoes a phase transformation from α- to β-phase at high hydrostatic pressures. The transition pressures for the three phases were calculated to be 380, 384 and 369 GPa by generalized gradient approximation, respectively; whereas according to the local density approximation results, they were 397, 412 and 400 GPa, respectively. The α- to β-phase transformation is generally accompanied by an increase of ∼0.8% in volume and an increased c/a ratio. Furthermore, the α- to β-phase transition also results in a reduction in the bulk modulus by<4%.

Keywords:

• High pressure
• Electronic structure
• Total energy
• MAX phases

Acknowledgements

We acknowledge the support from the Swedish Research Council (VR), STINT and SIDA.