Phase stability and elastic properties of CuGaSe2 under high pressure

• Stable phases of CGS under pressure are Amm2 and P4/mmm, which Cu and Ga sites can be distinguished from Fm-3m and Cmcm space groups.
• Phonon dispersions show phase stability in P4/mmm and Amm2, while pressure increasing gave the hardening of phonon vibration modes in CGS.
• Amm2 and P4/mmm are mechanically stable phases, while B/G ratios indicate that CGS in these structures are ductile material.
• The strong of covalent bond in CGS increases under high-pressure.

We report stability of high pressure phases and elastic properties in CuGaSe2, especially in cubic and orthorhombic phases. The distorted structures from Fm3¯m and Cmcm consist of Pmmn, P21/m, Amm2 and P4/mmm   were observed. Cu and Ga sites in Fm3¯m and Cmcm can distinguish in the lower symmetry space groups which are P4/mmm and Amm2, respectively. The enthalpy differences of an interested structure are compared in the pressure range 0–100 GPa. The phonon dispersion relation of CuGaSe2 was studied, and found that the P4/mmm and Amm2 space groups give stability of phonon vibration modes. Moreover, we observe chemical bonds and elastic properties of CuGaSe2 at high-pressure conditions. Elastic constants indicate mechanical stability of CuGaSe2 in P4/mmm and Amm2 phases. Although CuGaSe2 has become nonsemiconductor material in the P4/mmm and Amm2 phases, the strong of covalent bonds and sharing electrons are still increased by high pressure effect.