First-principles study the effect of anion position on physical properties of CuGaSe2

Abstract The electronic and optical properties of CuGaSe2 with different anion positions have been investigated by the first principles calculations. The crystal structures are optimized by two different methods, namely fixing the tetragonal distortion and constraining the fractional position of anion only. The optimized lattice parameters are slightly inconsistent with the results proposed by Abrahams and Bernstein. The band structure, density of states, dielectric functions, absorbance and reflectivity are calculated, using the modified Becke Johnson (mBJ) potential. CuGaSe2 with different anion positions are direct-gap semiconductors. When the anion position changes from 0.2 to 0.3, CuGaSe2 has strong absorption capacity, low reflectivity in visible light range and wide adjustable band gap, which means we can optimize the properties of CuGaSe2 by controlling the fractional position of anion.