STRUCTURES OF SI-10 - ARE THERE CONVENTIONALLY BONDED LOW-ENERGY ISOMERS

Accurate quadratic configuration-interaction calculations including the effects of triple excitations have been performed on different isomers of Si10. In agreement with previous studies, a tetracapped trigonal prism (C3v) is slightly more stable (0.3 eV) than a tetracapped octahedron (T(d)). Both these compact structures involving polyhedral bonding are considerably more stable (2.5 eV) than a conventional tetrahedrally bonded D2h Structure proposed recently by Messmer and Patterson. in addition, the D2h isomer is not a local minimum and collapses to a polyhedrally bonded C2h structure which is 1.6 eV less stable than the C3v form.