Theoretical investigation of geometry and stability of small lithium‐iodide Li n I ( n = 2–6) clusters

We present theoretical investigation of the structural characteristics and stabilities of neutral and positively charged Li n I ( n = 2‐6) species. The structural isomers were found by using a randomized algorithm to search for minima structures, followed by B3LYP optimizations; the single‐point RCCSD(T)/cc‐pwCVTZ(‐PP) calculations were performed in order to compute relative energies, binding energies per atom, adiabatic and vertical ionization energies, and dissociation energies. Stability was compared to the pure lithium clusters; there is a typical odd‐even alternation; iodine doped clusters are more stable than pure lithium clusters. Lithium “cage” transfers its valence electron to the iodine atom to form neutralI − − L i n +and cationicI − − L i n 2 +clusters. An electron departures the lithium cage upon ionization. An important reason for the larger stability of closed‐shell species is the existence of the HOMO 3c/2e natural bond orbitals. © 2013 Wiley Periodicals, Inc.