Comment on ‘A theoretical study of distortions induced by finite size in regular clusters’ (Julg, Del Re and Barone 1977)

Abstract

Abstract Using a simple self-consistent semi-empirical calculation method, Julg, Del Re and Barone observed some rounding off at the corners and along the edges of finite, highly symmetrical, lithium-like clusters. By extending their studies to infinite clusters, it is now shown that, above a critical size of the clusters, the corner atom has no symmetrical position consistent with the calculated bond distances. This phenomenon is called the ‘corner-atom dilemma’, and it is shown that the corner, edge and surface rearrangements of certain crystalline solids can be readily modelled with the above simple semi-empirical method. Certain ‘microwave’ experiments are proposed to observe the corner-atom dilemma on a stepped crystal surface in an oriented external electric field. The purpose of this paper is fivefold: (1) to complete the results of Julg et al. obtained for the distorted geometries of lithium-like finite clusters with the distorted geometries of infinite ones; (2) to discover the appearance of the corner-atom dilemma above a critical size of the clusters; (3) to show that certain corner, edge and surface rearrangements can be modelled with a very simple self-consistent semi-empirical method; (4) to propose the observation of the corner-atom dilemma by ‘microwave’ experiments; and (5) to present a few comments to justify the methods applied.