ROLE OF SELF-INTERACTION EFFECTS IN THE GEOMETRY OPTIMIZATION OF SMALL METAL-CLUSTERS

By combining the Self-Interaction Correction (SIC) with pseudopotentia l perturbation theory, the role of self-interaction errors inherent to the Local Density Approximation (LDA) to Density-Functional Theory is estimated in the determination of ground-state and low-energy isomeri c structures of small metallic clusters. Its application to neutral so dium clusters with 8 and 20 atoms shows that the SIC provides sizeable effects in Na-8, leading to a different ordering of the low-lying iso meric states compared with ab initio LDA predictions, whereas for Na-2 0 the SIC effects are less pronounced, such that a quantitative agreem ent is achieved between the present method and ab initio LDA calculati ons.