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