AB-INITIO MODELS FOR ZNS SURFACES - INFLUENCE OF CLUSTER-SIZE ON SURFACE-PROPERTIES

The feasibility of the cluster method is studied using two-dimensional ZnS surface models. We used the translational symmetry of electron in tegrals in the Hartree-Fock valence method as it enables studies of la rge systems, containing several hundred atoms. The results show that t he influences of boundaries and empty vacancies are limited only to a small area, and thus relatively small models can be used to simulate i nfinite systems. The properties are converging monotonically as the si ze of the model increases. However, in some cases small, size-dependen t variations exist. Augmenting the minimal valence basis set with Zn 4 p polarization functions decreases the influence of boundaries, and th e charge distribution of surface becomes more uniform.