(PbS)32: A baby crystal

Theoretical calculations based on density functional theory have found (PbS)32 to be the smallest cubic cluster for which its inner (PbS)4 core enjoys bulk-like coordination. Cubic (PbS)32 is thus a “baby crystal,” i.e., the smallest cluster, exhibiting sixfold coordination, that can be replicated to obtain the bulk crystal. The calculated dimensions of the (PbS)32 cluster further provide a rubric for understanding the pattern of aggregation when (PbS)32 clusters are deposited on a suitable surface, i.e., the formation of square and rectangular, crystalline nano-blocks with predictable dimensions. Experiments in which mass-selected (PbS)32 clusters were soft-landed onto a highly ordered pyrolytic graphite surface and the resulting aggregates imaged by scanning tunneling microscopy provide evidence in direct support of the computational results.