Study of the crystal structure and mechanical properties of ZrTi2 under pressure

Abstract

The pressure-induced modifications in the crystal structure and mechanical properties of ZrTi2 have been systematically studied by using the first-principle methods. The calculation of the enthalpy of formation was carried out using an efficient evolutionary algorithm at different pressures, as implemented in the USPEX code. The results revealed that the P6mm (space group #183) are stable at 0 GPa and it change rapidly to space group #164 close to 0 GPa and then at a pressure around 2 GPa to up around 60 GPa, the most stable phase is the crystal structure P63/mmc with the space group #194. Finally, the space group #164 returns to its stability between 60 and 100 GPa.The elastic constants obtained suggest that α— ZrTi2 (space group #194), P-3m1 (space group #164), and P6mm (space group #183) are mechanically stable at 0 GPa, while the space group #194 and #164 are stable in the other pressures evaluated (25, 50, 75, and 100 GPa). Finally, the β-ZrTi2 phase (space group #229) and ω—ZrTi2 (space group #191) showed a high enthalpy of formation with respect the other phases analyzed.