A series of  ab initio  Hartree-Fock calculations was performed for clusters which simulated the local environment of an interstitial in the 2 types of tetrahedral cavity in the zincblende structure. Neutral interstitial atoms of Li, Be, excess B, C, O, Si, and S were considered; with relaxation of the first-nearest and second-nearest neighbor shells of the atoms around the interstitials being allowed. The results predicted absolute stability only for Li and Be in the B-coordinated cavity. However, the present model had a number of limitations. Apart from the limitations of cluster size and configuration, and basis-set size, it was unclear whether the so-called breathing type lattice distortion was the most appropriate. In the case of interstitials with a larger radius, such as Si, severe lattice disruption could be required in order to accommodate the interstitial.

I.A.Howard: Solid State Communications, 1996, 99[10], 697-700