Gold and platinum microclusters and their anions: Comparison of structural and electronic properties

Abstract

We present a study of Au2 to Au5 and Pt2 to Pt5 clusters within density-functional theory in the neutral and anionic states. Results obtained using two exchange-correlation (xc) functionals, local spin density approximation and spin-polarized Becke-Lee-Yang-Parr (BLYP), are compared. The structural characteristics and relative stabilities of different isomers as well as electron affinities and vertical detachment energies are calculated. The latter compare generally well with experimental data, especially in the BLYP case. However, strong dependence of the vertical electron detachment energies on the isomer and on the xc-functional scheme indicates that special care must be taken for any comparison of theoretical results with experiment. Both for platinum and gold tetramers and pentamers, 3D geometries are unfavored. Triplet states are predicted to be more stable than singlets for platinum, for all sizes considered. The relative stability of different geometrical isomers is strongly affected by the addition of one electron. Marked differences emerge in the electronic structure between the clusters of these two metals. (C) 2000 Elsevier Science B.V.