Optical band gap and blue-band emission of aLiInS2single crystal

We report on the optical band gap of ${\mathrm{LiInS}}_2$, which comprises the pseudowurtzite structure in an orthorhombic unit cell. The band-structure nature of ${\mathrm{LiInS}}_2$ is confirmed to be direct with a forbidden gap of 3.73 eV at 77 K. The fundamental absorption edge is shifted to the lower energy by 160 meV at 300 K. In the photoluminescence study at 13 K a blue-band emission is observed at around 460 nm (2.70 eV), which has been assigned as a donor (sulfur vacancy or its complex) -valence-band transition, but the band-edge emission corresponding to the optical band gap is not found.