Dedicated global optimization search for ground state silica nanoclusters: (SiO2)(N) (N=6-12)

Employing a polyatomic version of the basin hopping global optimization algorithm, together with interatomic potentials specifically tailored to accurately describe the structures and energetics of nanoscale silica, a large number of energetically low-lying nanoclusters for (SiO2)N (N = 6−12) was generated. Substantial subsets of particularly low-energy candidate structures for each cluster size were subsequently further evaluated using density functional theory (DFT) energy minimization calculations. We report the resulting lowest energy nanoclusters, together with the energetically nearest lying nanoclusters, for each cluster class, (SiO2)N (N = 6−12). The majority of the clusters obtained display no structural motifs typical of bulk crystalline silica. Of all the clusters studied, the lowest energy (SiO2)8 cluster found is shown to be especially thermodynamically favored compared to other similarly sized cluster isomers and with respect to addition or removal of SiO2 units. The clusters are discussed with respect to their structure, their reactivity, and their suitability as building blocks for new materials.