<i>Ab initio</i>molecular-dynamics studies of doped magic clusters and their interaction with atoms

Abstract

We present results of the atomic and electronic structure of icosahedral ${\mathrm{Al}}_{12}X$ $(X=\mathrm{S}\mathrm{i}$, Ge, and Sn) clusters using the ab initio molecular-dynamics method within the local density functional theory. Substitutional doping of a ${\mathrm{Al}}_{13}$ cluster by a tetravalent atom leads to a substantial gain in energy in all the cases studied. Tin is found to have a lower energy at a vertex site in contrast to the central site for Si and Ge, leading to surface segregation of Sn in these clusters. Also in the case of a ${\mathrm{Al}}_{13}\mathrm{Si}$ cluster, Si occupies the central site of a capped icosahedral structure. These results when interpreted in terms of the interaction of closed shell clusters with atoms leads to a relatively strong interaction of ${\mathrm{Al}}_{12}\mathrm{Si}$ with $\mathrm{Al}$ as compared to the weak interaction of rare gas atoms with other elements.