First-principles study of the elastic, electronic and optical properties of ε-GaSe layered semiconductor

The elastic, electronic and optical properties of ε-GaSe layered semiconductor have been studied from the first principles with the local density approximation (LDA). The optimized structure of GaSe has been found to be in good agreement with the experimental results. The mechanical stability of ε-GaSe is confirmed by calculations of the elastic constants. The calculated band structure shows that the crystal has a direct band gap of 0.816 eV. Furthermore, the linear photon-energy-dependent dielectric functions and some optical constants such as refractive index, extinction, reflectivity and absorption coefficients have been calculated.