A theoretical study of distortions induced by finite size in regular clusters

Abstract

An iterative molecular orbital method is applied to lithium-like metal clusters. An iteration procedure based on a linear relationship between bond orders and interatomic distances for nearest neighbours allows determination of the equilibrium geometries. One-dimensional chains, two-dimensional squares, rectangular and triangular arrays, cubes, parallelepipeds, and tetrahedra with increasing numbers of centres are examined. Considerable distortions appear with respect to regular infinite lattices. The average bond lengths tend to increase with increasing sizes of the clusters, the external bonds being shorter than the inner ones, so that some rounding off at the edges and corners is found. In many cases, lower symmetry structures are expected to be more stable than higher symmetry ones.