Abstract
In this work, the electronic and optical properties of FA center at the LiF (001) surface were investigated by using density functional theory (DFT) and configuration interaction single (CIS) excitations methods. Three species of alkali earth metals, Be, Mg, and Ca, were
used as dopants to form three FA centers namely, FA: Be+2, FA: Mg+2, and FA: Ca+2 LiF centers. The calculated values of the ionization potential (IP), electron affinity (eA), and the chemical hardness (η)
indicate that the FA: Be+2 center is more stable than both of FA: Mg+2, and FA: Ca+2 centers. The density of states (DOS) calculations reveal that the presence of FA color center creates a localized electronic states
which in turn decrease the HOMO-LUMO gap to be 2.88, 2.65,and 2.41 eV for FA: Be+2, FA: Mg+2, and FA: Ca+2 LiF centers, respectively. The UV-Vis spectra calculations for the studied centers show that both of FA: Be+2
and FA: Mg+2 centers have two absorption peaks, at 212and 321 nm for the former and 249 and 343 nm for the later while FA: Ca+2 center has only one strong peak at 339 nm. The stokes-shift values for FA: Be+2, FA:
Mg+2, and FA: Ca+2 centers were 0.74, 0.68, and 0.27 eV,respectively. Our obtained results may be helpful for utilizing the LiF crystal defected by FA: Be+2, FA: Mg+2, and FA: Ca+2 centers for
laser light generation.