Global minima of (C60)nCa2+, (C60)nF- and (C60)nI- clusters

Likely candidates for the lowest potential energy minima of (C-60)(n)Ca2+, (C-60)(n)F- and (C-60)(n)I-, clusters are located using basin-hopping global optimisation. In each case, the potential energy surface is constructed using the Girifalco form for the C60 intermolecular interaction, an averaged Lennard-Jones C-60-ion interaction, and a polarisation potential, which depends on the first few non-vanishing C60 multiPole polarisabilities. We find that the ions generally occupy the interstitial sites of a (C-60)(n) cluster, the coordination shell being tetrahedral for Ca2+ and F-. The F ion has an octahedral coordination shell in the global minimum for (C-60)(6)I-, however for 12 >= n >= 8 the preferred coordination geometry is trigonal prismatic. (c) 2005 Elsevier B.V. All rights reserved.