Computer Simulation of the Electronic Structures and Absorption Spectra for a KMgF₃ Crystal Containing a Potassium Vacancy

CASTEP code, based on the density functional theory (DFT) Electronic structures and absorption spectra for a perfect KMgF₃ crystal and a KMgF₃ crystal containing a potassium vacancy V_K⁻ are optimized using the CASTEP density functional theory code. The calculated results indicate that the perfect KMgF₃ crystal has no absorption in the visible energy region, however, a KMgF₃ crystal containing V_K⁻ has an additional absorption band peaking at 565 nm, fitting well with the experimental result that KMgF₃ irradiated by an electron has an additional absorption peak at 565 nm. It is reasonably predicted that the 565 nm absorption band is related to the existence of V_K⁻ in the KMgF₃ crystal created by the electron irradiation.