We have performed a systematic ground state geometry search for ${\mathrm{Ge}}_n$ neutrals and cations in the $n\le 16$ 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 ${\mathrm{Ge}}_n$ and ${\mathrm{Si}}_n$ for $n=13\mathrm{}$ and $n\ge 15$ 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.

• Received 16 February 1999

DOI:https://doi.org/10.1103/PhysRevLett.83.2167