Electron spin resonance parameters of bulk oxygen vacancy in semiconducting tin dioxide

We present density-functional theory calculations of the electron spin resonance g and hyperfine coupling A tensors in cluster models of a positively charged oxygen vacancy VO⁺ in semiconducting tin dioxide, SnO₂. Convergence of the results with the cluster size, basis set, choice of exchange-correlation functional, and choice of the method of the cluster termination by either pseudohydrogen atoms or electrostatic embedding, are investigated. The results agree with two of the earlier experimental assignments of the g value around 2.00, whereas in the case of other experiments $(g=1.89)$, a reassignment is suggested. We also investigate the energy levels of the impurity states via the Kohn-Sham orbital energies of the defect-free bulk, positively charged vacancy (VO⁺), and neutral vacancy (VO⁰) structures.