F2+ defect based model for tunable laser activity and interaction of atomic halogens (F, Cl and Br) at the low coordinated surfaces of LiH: ab initio calculations

The twofold potential of F2+ color center at the low coordinated surfaces of LiH in providing tunable laser activity and adsorption properties for atomic halogens is examined using ab initio calculations. Based on Stokes shifts of the examined clusters, the F2+ laser activity was very weak, but increases significantly as the coordination number decreases from 5 (flat) to 4 (edge) to 3 (H− corner). The corner site is the least probable for relaxed excited state orientational destruction of F2+. The exciton (energy) transfer takes place from the corner to the flat or edge sites. The Glasner–Tompkins relation is generalized to include the low coordinated surfaces of LiH. The F+2 color center change the nature of halogen–surface interaction from physical adsorption to chemical adsorption. The halogen–surface interactions were monotonically increasing functions of the electronegativity of the halogen and the amount of charge transferred between the halogen and the surface. The “covalent spin pairing” mechanism play the dominant role in the course of adsorbate–substrate interactions.