Study on the absorption spectra and electronic structures of the CsI crystal with cesium vacancy

The electronic structures and absorption spectra of the perfect CsI crystal and the CsI crystal containing Vcs1- have been calculated using CASTEP code with the lattice structure optimized. The calculated results indicate that the optical symmetry of CsI crystal coincides with the lattice structure geometry of CsI crystal. The perfect CsI crystal has no absorption band in the visible region. However, the absorption spectra of the CsI crystal containing Vcs1- exhibit two peaks at 2.21 and 3.00 eV in the visible and near-ultraviolet region, which are caused by Vcs1-.