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 ${\mathrm{Zn}}_i{X}_i$ clusters are studied, $X=\mathrm{S}\mathrm{e},\mathrm{T}\mathrm{e},$ $i=1\mathrm{}–9.$ Ringlike structures have been found to be the global minima for clusters as large as $i=5,$ and three-dimensional spheroid structures for larger ones, $i=6\mathrm{}-9.$ This trend has been ascribed to the stability of obtuse $X-\mathrm{Zn}-X$ 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 ${\mathrm{Zn}}_2{X}_2$ and ${\mathrm{Zn}}_3{X}_3$ rings, as it was the case for ${\mathrm{Zn}}_i{\mathrm{S}}_i$ and ${\mathrm{Zn}}_i{\mathrm{O}}_i$ three-dimensional structures. Calculated natural charges are larger as cluster size increases, showing a tendency towards bulk charges.

• Received 26 March 2001

DOI:https://doi.org/10.1103/PhysRevA.64.053201