Structures of germanium clusters: Where the growth patterns of silicon andgermanium clusters diverge

We have performed a systematic ground state geometry search for Ge, neutral s and cations in the n less than or equal to 16 size range using density fu nctional theory-local density approximation and gradient-corrected methods. Like their silicon analogs, medium-sized Ge clusters are stacks of tricapp ed trigonal prism subunits. However, the structures of Ge-n and Si-n for n = 13 and n greater than or equal to 15 differ in details. The onset of the structural divergence between the growth patterns of Si and Ge clusters is confirmed by the measurements of gas phase ion mobilities, fragmentation pa thways, and dissociation energies.