The structures of B7, B10 and B13 boron clusters are studied using the full-potential linear-muffin-tin-orbital molecular-dynamics method. Seven stable structures for B7 and fifteen for B10 have been obtained. C2h-B10 is the most stable among the 15 structures, but C2v-B10 is not stable. For B13, three degenerate ground-state structures have been found. The potential surface near C2v-B7 (ground state) and D6h-B7 is very flat. As a fundamental unit in constructing bigger clusters, C2v-B7 will change its form easily. The most stable structures for B7, B10 and B13 clusters are two-dimensional (quasi-) planar clusters, rather than the three-dimensional ones. General speaking, these clusters obey the `Aufbau principle'.

PACS 61.46.+w, 71.15.Pd, 73.22.Dj Using full-potential linear-muffin-tin-orbital molecular-dynamics (FP-LMTO-MD) method, we have studied the geometric and electronic structures of ionic Si 2-10 clusters. The structures we obtained include not only all the most stable structures reported previously, but also some new structures. Our calculations show that the ground state structure of negative Si 8 -cluster ion is a new structure with C 2v , which is different from that reported before. In addition, we have also found that the ground state structure of positive Si + 10 cluster ion is a tricapped pentagonal bipyramid with C s symmetry, which has been not reported previously. As for their electronic structures, these charged silicon clusters show 0.5 -2.5 eV of energy gaps between the lowest unoccupied energy level and the highest occupied energy level. The gaps for cationic silicon clusters are closer to those of their corresponding neutral clusters, but many of the gaps for the anionic clusters are not.

The structure and geometrical parameters for water adsorption on a small-silicon-cluster surface have been studied using the linear-muffin-tin-orbital method. We find that the most favoured adsorption site is the atop site of the capped atom for , and clusters. When adsorbs at such sites, the silicon clusters are elongated in the direction of the axis connecting one capped atom to another capped atom. Also, saturation studies have been performed. Each of these clusters can only adsorb two molecules at two atop sites of capped atoms. These clusters cannot adsorb any more molecules.

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The adsorption and the surfactant effect of Sb on the Ag(100) surface are studied using first-principles calculations. Our calculated results show that the pre-adsorbed Sb atoms act as nucleation centres for the deposited Ag atoms, and surface-substitutional Sb atoms repel on-fcc-site Ag atoms nearby. We suggest that the Sb repulsion network reduces the Ag-adatom mobility and leads to a high density of Ag islands which improve the smoothness of the layer-by-layer growth.