Electronic structure of LiGaS2

X-ray photoelectron spectroscopy (XPS) measurement has been performed to determine the valence band structure of LiGaS2 crystals. The experimental measurement is compared with the electronic structure obtained from the density functional calculations. It is found that the Ga 3d states in the XPS spectrum are much higher than the calculated results. In order to eliminate this discrepancy, the LDA+U method is employed and reasonable agreement is achieved. Further calculations show that the difference of the linear and nonlinear optical coefficients between LDA and LDA+U calculations is negligibly small, indicating that the Ga 3d states are actually independent of the excited properties of LiGaS2 crystals since they are located at a very deep position in the valence bands.