Electronic structure, bonding, and properties of SnmGen (m + n ⩽ 5) clusters: A DFT study

Electronic structures of tin–germanium binary clusters up to five atoms obtained by searching global optimization of the energy surface using Metropolis Monte Carlo (MMC) and genetic algorithm (GA) followed by bond strength propensity model (BSPM) and by local optimization using density functional theory (DFT) are reported. Geometries and properties of the most stable cation, neutral, and anion clusters are calculated at the B3LYP/aug-cc-pVTZ-pp level of theory. The average binding energy per atom is calculated to study its dependence on the size of the cluster. The HOMO–LUMO energy gap, ionization potential (IP), electron affinity (EA), and vertical detachment energy (VDE) are also computed for the most stable isomer of each cluster. The reactivity descriptors such as chemical potential, chemical hardness, and electrophilicity index of the lowest-energy isomers of these clusters are estimated to study their relative stabilities. The one-step fragmentation patterns of the clusters are studied to determine the relative strength of the Ge–Ge, Sn–Ge, and Sn–Sn interactions by computing the fragmentation energies. A four membered ring formed by the Sn2Ge2-b cluster shows π-aromaticity with a NICS(1) value of −13.2 ppm.