SEMIEMPIRICAL MOLECULAR-ORBITAL CALCULATION OF GEOMETRIC, ELECTRONIC,AND VIBRATIONAL-STRUCTURES OF METAL-OXIDE, METAL SULFIDE, AND OTHER INORGANIC FULLERENE SPHEROIDS

We have performed semiempirical molecular orbital calculations, using the Austin Model 1# (AM1) and Parametric Method 3# (PM3) Hamiltonians of the program MOPAC for the geometric, electronic, and vibrational st ructure of(ZnO)(n) (where n = 1-16), spheroids, and (MX)(12) analogs, where M = {Be, Mg, Zn, Cd, Hg, Pb, Sn, Ge, Si, C} when X = {O-., S} an d where M = {B, Al} when X = {N, P}. Of these the symmetrical (ZnO)(n) (where n = 12 and 16) clusters are the most stable. All of the n = 12 analogs, including C-24, Si-24, and (SiC)(12), were studied under T-d (O-h) symmetry, where they were found to have stationary points on the electronic potential energy surface. Ab initio Hartree-Fock calculati ons done on (BeO)(12), (BN)(12), (MgO)(12), C-24 and (ZnO)(12), using the program GAUSSIAN 92, confirm this result. All compounds were vibra tionally stable except, unsurprisingly, (CO)(12), which has six negati ve eigenvalues of the Hessian matrix under both AM1 and PM3, while (Be O)(12) and (GeS)(12) have three negative eigenvalues under PM3 but are stable under AM1. Properties computed include bond lengths, bond angl es, bond orders, heats of formation, atom charges, valence electron or bital energies including HOMO and LUMO band separation energy, and vib rational normal mode frequencies.