Small clusters of II-VI materials: ZniSi,i=1–9

The improvements in the characterization of II-VI compound-based solar cells and the recent experimental characterization of small clusters and nanoparticles make the study of small II-VI clusters very interesting. In this work, the ground states of small ${\mathrm{Zn}}_i{\mathrm{S}}_i$ clusters are studied, $i=1\mathrm{}–9.$ Ringlike structures have been found to be the global minima in the case of the smaller studied clusters, i.e., $i=1\mathrm{}–5,$ and three-dimensional spheroid structures for larger ones, $i=6\mathrm{}–9.$ This is due to the stability of obtuse $\mathrm{S}\mathrm{—}\mathrm{Zn}\mathrm{—}\mathrm{S}$ angles in the first case, and to the stability gained from higher coordination in the second case. The three-dimensional structures may be envisioned as being built from ${\mathrm{Zn}}_2{\mathrm{S}}_2$ and ${\mathrm{Zn}}_3{\mathrm{S}}_3$ rings, the last ring being the building block of the zinc-sulfide crystal structures, both zinc blende and wurtzite. As cluster size increases, the geometry of the ${\mathrm{Zn}}_3{\mathrm{S}}_3$ rings is closer to the one of bulk. Moreover, this structural tendency produces trends to bulklike properties in other properties such as cohesive energy and atomic charges.