A theoretical investigation on geometry and electronic structure of small FemSn nanoclusters (1 ≤ m, n ≤ 4)

The equlibrium structure and relative stability of FemSn clusters (1 <= m,n <= 4) were investigated using density functional theory and second order Meller-Plesset perturbation theory. In general, the S doping leads to significant changes in the geometry of the studied clusters. It is evident that the Fe-Fe distances are elongated upon the sequential addition of sulfur. Relative stabilities of these clusters were analyzed based on the variation of their averaged binding energies, and Fe-S bond formation energies. Based on quantum theory of atoms in molecules (QTAIMs), the non-covalent character of the Fe-S bond is increased in the FemSn clusters as the corresponding bond critical points (BCPs) showed more positive del(2-) rho(BCP) value than those of the FeS molecule. On the other hand, the estimated electron charge density values at Fe-Fe BCPs lie in the order of 0.11-0.22 au. The corresponding Laplacian values in all clusters are negative and are the result of the interaction between two open-shell systems. (C) 2012 Elsevier B.V. All rights reserved.