First-principles investigation of structural phase transitions and electronic properties of CuGaSe2 up to 100 GPa

First-principles calculations based on density functional theory have been carried out for the photovoltaic material CuGaSe2 up to 100 GPa to clarify its possible structural phase transitions and electronic properties. Energy–Volume analysis confirms that CuGaSe2 transforms from the tetragonal I 4 ¯ 2 d structure to the cubic Fm 3 ¯ m structure at 11.87 GPa with a volume reduction of 13.33%, which are in fair agreement with the experimental results of 13 GPa and 13%, respectively. We also predict another phase transformation of CuGaSe2 from the cubic Fm 3 ¯ m structure to the orthorhombic Cmcm structure at 51.4 GPa with a volume reduction of 0.49%. By using the HSE functional for Gap–Pressure analysis, we find that the energy gap of I 4 ¯ 2 d structure broadens at a rate of 52.3 meV/GPa. By the band structure and the density of states calculation, we predict the metallic nature of the Fm 3 ¯ m and Cmcm phases and discuss the original reason of metallic nature under high pressure by the calculation of bond lengths and the charge redistribution.