Ab initio calculations were performed for X+(H-2)(n) clusters [X=Li, Na (n=1-7) and K (n=1-3)]. For n=1-6, the equilibrium geometries correspond to spherically symmetrical distributions of H-2 units around the X+. The binding energies and the geometric parameters indicate that the seventh H-2 unit opens a new shell of ligands for the cluster with X=Li but not for X=Na. (C) 2001 American Institute of Physics.