Density functional theory techniques were used to investigate the defect structure of X- (X = O, S, Se) ions in MZ (M = Na, K, Rb and Z = Cl, Br) alkali halides which exhibited monoclinic-I g-tensor symmetry, using cluster in vacuo, embedded cluster, and periodic embedding schemes. Although a perturbed interstitial defect model was suggested from electron paramagnetic resonance experiments, the nature of the perturbation was still unknown. An appropriate defect model was developed theoretically by comparing structural and energetical properties of various defect configurations. Further validation was achieved by cross referencing experimental and computed electron paramagnetic resonance data. On the basis of the computational results, the following defect model was proposed: the X- ion was located interstitially with a charge compensating halide vacancy in its first coordination shell.

X- (X = O, S, Se) Ions in Alkali Halide Lattices Through Density Functional Calculations - Interstitial Defect Models. V.Van Speybroeck, F.Stevens, E.Pauwels, H.Vrielinck, F.Callens, M.Waroquier: Journal of Physical Chemistry B, 2006, 110[16], :8213-8