Chemical reactivity and covalent-metallic bonding ofSin+(n=11–25) clusters

Abstract

Using our earlier thermodynamic force field we have calculated the equilibrium structures of medium-size ${\mathrm{Si}}_{\mathrm{n}}$ clusters (n=1–25). We find the very surprising result that beginning at n=7, near n=13 and near n=19, these clusters follow a pentagonal growth pattern (icosahedra plus associated face capping). Our results are fully consistent with magic numbers recently found in the reaction rates for addition of first ${\mathrm{C}}_2$ ${\mathrm{H}}_4$ molecules to ${\mathrm{Si}}_{\mathrm{n}}^{+}$ clusters.