Size Effect on the Structural and Electronic Properties of Lead Telluride Clusters

Theoretical computations of (PbTe)(n) (n = 21-45) clusters based on density functional theory have demonstrated that at cluster size of (PbTe)(22) there is a transition from the strong preference of fivefold coordination to sixfold coordination of lead and tellurium atoms. (PbTe)(24) cluster is the smallest tetragonal structure in which its central atoms have bulk-like coordination. This quantum dot (QD) contains a single-unit cell of lead telluride crystal, thus can be considered as an " infant crystal." (PbTe)(32) cluster is a perfectly cubic cluster for which its inner (PbTe)(4) core enjoys bulk-like coordination. This (PbTe)(4) core unit of (PbTe)(32) cubic cluster has exactly the same environment as a primitive cell of lead telluride crystal. The (PbTe)(8n), (n >= 3) clusters are the magic number species with bulk-like structure such that (n = 3-5) the nanoblocks considered here (PbTe)(24), (PbTe)(32), and (PbTe)(40) clusters exhibiting bulk-like structure that can be replicated to obtain the bulk crystal. The calculated dimensions of this special clusters provided a rubric for understanding the pattern of aggregation, that is, the creation of defined nanoblocks [(PbTe)(8n), (n = 6)], when they were accumulated on an appropriate surface. It is evident that the QDs (PbTe)(8n), (n = 3-5) clusters show high stability compared to their neighboring clusters. This can also be seen from the second-order energy difference, binding, and fragmentation energy graphs. (C) 2014 Wiley Periodicals, Inc.