Lowest-energy structures of (MgO)n (n = 2–7) clusters from a topological method and first-principles calculations

A topological method combined with first-principles calculations is used to generate isomer structures and to globally search on the potential energy surface of (MgO)n clusters with n = 2–7. In addition to the previously reported ground-state configurations, our approach has located many new metastable isomer structures. The growth pattern of MgO clusters can be classified into three motifs: the expansion of two-dimensional ring-like structures, the combination of basic units like quadrangle and hexagon, and the addition of atoms to smaller-sized clusters. The size-dependent stability and electronic properties of MgO clusters are analyzed. Hexagonal ring-like unit is found highly stable for (MgO)n clusters, while the (MgO)5 cluster is not as stable as the clusters of other sizes.