Electron-correlation energies and the structure ofSi13

A simple physical model for the difference in correlation energies of ${\mathrm{Si}}_{13}$ in icosahedral and trigonal prismatic structures yields semiquantitative estimates for this difference, which show that it can stabilize the icosahedral structure relative to the trigonal one by as much as 0.2 eV/electron, or ∼10 eV per cluster. The same model is compatible with a difference in reactivities between ${\mathrm{Si}}_{12}$ and ${\mathrm{Si}}_{13}$ of order ${10}^3$, in agreement with experiment.