Magic Numbers of Silicon Clusters

TL;DR

This paper introduces a structural model for intermediate-sized silicon clusters that predicts unique, stable configurations without dangling bonds, explaining their chemical inertness and shape transitions observed experimentally.

Contribution

The paper proposes a new structural model for silicon clusters that accounts for their stability, shape transition, and reactivity, which was not previously understood.

Findings

Unique stable structures for Si33, Si39, Si45 without dangling bonds

Explains low reactivity towards certain chemisorption

Accounts for shape transition at Si27

Abstract

A structural model for intermediate sized silicon clusters is proposed that is able to generate unique structures without any dangling bonds. This structural model consists of bulk-like core of five atoms surrounded by fullerene-like surface. Reconstruction of the ideal fullerene geometry results in the formation of crown atoms surrounded by $\pi$-bonded dimer pairs. This model yields unique structures for \Si{33}, \Si{39}, and \Si{45} clusters without any dangling bonds and hence explains why these clusters are least reactive towards chemisorption of ammonia, methanol, ethylene, and water. This model is also consistent with the experimental finding that silicon clusters undergo a transition from prolate to spherical shapes at \Si{27}. Finally, reagent specific chemisorption reactivities observed experimentally is explained based on the electronic structures of the reagents.