Semiempirical molecular orbital calculation of geometric, electronic, and vibrational structures of metal oxide, metal sulfide, and other inorganic fullerene spheroids

Abstract

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 structure 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 and 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 calculations done on (BeO) 12, (BN) 12, (MgO) 12, C 24 and (ZnO) 12, using the program gaussian 92, confirm this result. All compounds were vibrationally stable except, unsurprisingly, (CO) 12, which has six negative eigenvalues of the Hessian matrix under both AM1 and PM3, while (BeO) 12 and (GeS) 12 have three negative eigenvalues under PM3 but are stable under AM1. Properties computed include bond lengths, bond angles, bond orders, heats of formation, atom charges, valence electron orbital energies including HOMO and LUMO band separation energy, and vibrational normal mode frequencies.