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

We have performed a systematic ground state geometry search for Ge, neutrals and cations in the n less than or equal to 16 size range using density functional theory-local density approximation and gradient-corrected methods. Like their silicon analogs, medium-sized Ge clusters are stacks of tricapped 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 pathways, and dissociation energies.