Abstract: FA1:Ag+ color center at the low coordination (100) and (110) surface sites of KCl
and KBr thin films play an important role in providing tunable laser oscillation and adsorbatesubstrate
interactions. Double-well potentials at this site are investigated using ab initio molecular
electronic structure calculations. The calculated Stokes shifted (optical transition bands), opticaloptical
conversion efficiencies, the probability of orientational destruction, exciton (energy) transfer
and Glasner–Tompkins empirical rule suggest that laser light generation is sensitive to (i) the
lattice anion, (ii) the coordination number of surface ions, and (iii) the choice of the basis set
centered on the anion vacancy. The adsorbate-substrate interactions were found to be dependent
on the electronegativity of the adatom and on the lattice anion. Optimised geometries and the
coadsorption of CO and (F, Cl, Br, I) on KCl and KBr (100) crystals are presented. Calculated
chemisorption energies for CO on the (halogen atom/defect free sites of KCl and KBr (100)
crystals) showed that the coadsorption of halogen atom tends to block other adsorbate-substrate
interactions at the nearest neighbour sites. Thus if halogen atom coverage increases, the CO
prefers to be adsorbed on the K+ site of the KCl and KBr (100) surfaces and on KBr relative to
KCl.