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

The total energy and geometry of nanoclusters 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 , while in others it is unique for each composition. We found that the ensemble of clusters remains uniform after passivation only if hydrogen concentration corresponds to one of the stable compositions???, , , or . 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 above the ground state. These metastable configurations come into existence in synthesis at , making experimentally realizable cluster compositions even more diverse.