CNDO/2 calculations of relaxation and reconstruction of diamond and silicon [111] surfaces

CNDO /2 calculations have been performed on the clusters X₄H₉ and X₄Y₉ modeling the [111] diamond and silicon surfaces. The X is either carbon or silicon atom and the Y is a pseudoatom containing one sp³ hybrid orbital. It is shown that in the CNDO /2 approximation in the foregoing pseudoatom models, the charge distribution of the cluster is better than the hydrogen atom, because the electronegativity of the hydrogen differs significantly from the electronegativity of the sp² orbital of the silicon atom. Using the CNDO /2 parametrization, the electronegativity of the hydrogen is very near to the electronegativity of the sp³ orbital of the carbon atom, thus the hydrogen can be used for the saturation of the carbon clusters.