Thermal effects in the equilibrium structure and size distribution of small Si clusters

We present the first calculation of the free energy of semiconductor clusters at nonzero temperatures. Explicit determination of electronic, vibrational, and rotational contributions to the entropy allows us to investigate the effect of temperature on the equilibrium geometric structure and size distribution of these clusters. The formalism is applied to ${\mathrm{Si}}_4$, ${\mathrm{Si}}_5$, and ${\mathrm{Si}}_6$ clusters with symmetric geometries. We find that, in these clusters, entropy can modify relative stabilities, but does not change major trends at finite temperatures.