A symmetric structure of the gas-phase H3+(H2)9 cluster

Structures of the gas-phase clusters, H-3(+)(H-2)(n) (n = 0-10) and binding energies of H-3(+)(H-2)(n) and D-3(+)(D-2)(n) (n = 1-9) were calculated with a modified G2 theory, called G2* here. Theoretical binding energies and their isotope effects are in good agreement with experimental data. Shell structures were examined carefully. The n = 7 cluster is the second half-shell where one H-2 molecule above the H-3(+)(H-2)(3) first solvation shell and three below the shell. The H-3(+)(H-2)(9) cluster is the complete second shell. The C-3-symmetry condition is required to form shells. Therefore, the 'magic number' n = 6 is not effective in the H-3(+)(H-2)(n) cluster. (C) 1998 Elsevier Science B.V. All rights reserved.