Abstract: A many-body expansion potential energy function is used to study the structures and stabilities of silicon microclusters,suggesting that firstly,Si₄-Si₁₆ clusters can be constructed by successively adding two-or three-coordinated atoms,forming surfaces covered with four-membered butterfly rings(D_2d);secondly,the trigonal bipyramid Si₅(D_3h) and D_2d Si₆ are the building blocks for most of these compact structures with a D_4d cage Si₁₀ added in for the clusters with over 10 atoms and both Si₁₀ and Si₁₆ are covered with three-or four-or five-coordinated atoms,predicting that Si₅,Si6,Si₁₀,and Si₁₆ be the prominent peaks in the mass spectra of fragmentized silicon clusters,in agreement with experiments;and finally,these nondiamond compact structures have a maximum coordination number of five and the formation of six-coordinated silicon centres within half a sphere leads to destablization in energy.

Key words: Many-body expansion potential energy function, Silicon clusters, Structures, Stabilities, Surface structures