Prediction of the atomic structure and stability for the ensemble of silicon nanoclusters passivated by hydrogen

The total energy and geometry of nanoclusters $\mathrm{Si}_{10}\mathrm{H}_{2m}\ (m=0\text{--}12)$ are calculated using evolutionary structure searching and density functional theory. The calculation shows that the arrangement of Si atoms is close to the diamond crystal structure only in the cluster $\mathrm{Si}_{10}\mathrm{H}_{16}$ , while in others it is unique for each composition. We found that the ensemble of $\mathrm{Si}_{10}$ clusters remains uniform after passivation only if hydrogen concentration corresponds to one of the stable compositions – $\mathrm{Si}_{10}$ , $\mathrm{Si}_{10}\mathrm{H}_{14}$ , $\mathrm{Si}_{10}\mathrm{H}_{16}\ \mathrm{Si}_{10}\mathrm{H}_{20}$ , or $\mathrm{Si}_{10}\mathrm{H}_{22}$ . Passivation by an arbitrary amount of hydrogen converts the ensemble into a mixture of the stable clusters having the nearest compositions. In addition there are numerous metastable cluster configurations with energies within $\sim0.1\ \text{eV}$ above the ground state. These metastable configurations come into existence in synthesis at $T\geq500\ \text{K}$ , making experimentally realizable cluster compositions even more diverse