Calculations were made, of the self-trapping properties of Al-Na centers in -quartz, by using a Mott-Littleton formulation. It was found that the hole in [AlO4/Na]0 was most energetically likely to self-trap at an O atom that was nearest to the Al ion with a so-called short bond. It was also found that the Na ion was in the nearby c-axis channel on the long-bond side of the Al ion. The calculated results agreed well with experimental data. It was also found that the hole was energetically likely to self-trap at an O ion which was next-nearest to the Al ion. The hole-trapping energies in the 2 cases were similar, and their sites could not be easily distinguished by experiment.

X.Zhang, C.K.Ong: Journal of Physics - Condensed Matter, 1995, 7[45], 8577-85