AB-INITIO POTENTIAL-ENERGY CURVES FOR LOW-LYING STATES OF CARBON-DISULFIDE

Potential energy surfaces for the ground singlet (S-0), lowest excited singlet (S-1), and lowest triplet (T-0) electronic states of carbon disulfide are explored using ab initio Hartree-Fock (HF), generalized valence bond (GVB) and multiconfiguration self-consistent-held (MCSCF) methods using the 6-31G* basis. The lowest singlet hypersurface, S-0, contains the linear (D-infinity h) equilibrium geometry ground state X (1) Sigma(g)(+) and the previously unreported bent (C-2 upsilon) conformer (1)A(1). The calculated geometry of the linear state [r,(C-S)=1.544 Angstrom] compares favorably with experiment [ro(C-S)=1.556 Angstrom]; there are no experimental values to compare with the calculated geometry of the bent state Cr,(d-s)=1.718 Angstrom, <SCS =78.4 degrees]. The transition state between the linear and bent conformers is determined to have C-2v geometry [r(C-S)=1.691 Angstrom, <SCS=103.4 Angstrom] and a barrier height of 7.7 kcal/mol. We also explore the B-1(2) surface, S-1, and the B-3(2) surface, T-O, finding the equilibrium geometry, dipole moments, and vibrational frequencies of these states as well as those of the ground state and bent conformer.