Band gaps of CaX (X=S, Se, Te) in GW approximation correction

Abstract:

The structures and electronic properties of calcium chalcogenides CaX (X=S, Se, Te) in NaCl structure have been investigated by using the first-principle pseudopotential method based on density function theory within a LDA (local density approximation). The calculated lattice parameters are in excellent agreement with the experimental results, whereas the minimum gaps are much lower than the experimental ones. To get the reliable band gap values, we employ the GW (G is Green’s function and W is the screened Coulomb interaction) approximation method to correct the band gap values. The band gap values of CaS and CaSe using GW approximation have been improved compared to the obtained results from the LDA, which are in agreement with the experimental data. And we also predict the band gap value of the CaTe. It is expected that GW approximation should be very appropriate, though there is no experimental result for CaTe.