ELECTRON-CORRELATION EFFECTS ON GEOMETRICAL AND ELECTRONIC STRUCTURES OF SinNa CLUSTERS
The geometries and energies of silicon-sodium binary clusters ( Si n Na , n=2–7) were investigated with the inclusion of electron-correlation effects using the second-order Møller–Plesset perturbation theory (MP2) with the 6-31G basis set. In addition, the fourth-order (MP4) energies were evaluated to determine the ground-state isomers. Si 4 Na cluster was calculated with the polarized 6-31G* basis set. For all of the Si n Na clusters, the most stable isomers have bridge-site type structures. Apart from the bridge-site type Si 6 Na , the structure of the most stable isomer of SinNa keeps the frame of the corresponding Si n cluster unchanged, and the electronic structure of Si n Na is similar to that of the corresponding negative ion [Formula: see text]. The silicon framework of the bridge-site type of Si 6 Na is distorted from the compressed octahedron to the face-capped trigonal bipyramid.