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