Je. Stevens et al., EXCITED POTENTIAL-ENERGY SURFACES OF CH3SH FROM THE AB-INITIO EFFECTIVE VALENCE SHELL HAMILTONIAN METHOD, The Journal of chemical physics, 101(6), 1994, pp. 4832-4841
The ground and first and second (1)A'' potential surfaces of methyl me
rcaptan (CH3SH) are calculated as a function of the C-S and S-H bond c
oordinates using the ab initio effective valence shell Hamiltonian (H(
n)u) method. The computations for this highly nontrivial system provid
e the first serious tests for choosing restricted valence spaces and f
or computing global potential energy surfaces with the H(n)u methods.
The quasidegeneracy constraints on the H(n)u method suggest choosing a
valence space which consists of the two (3a'' and 10a') highest energ
y occupied orbitals in the ground state and the three lowest a' unoccu
pied orbitals. The global potential surfaces are computed with a modes
t basis, but larger basis set computations at selected geometries test
convergence for vertical excitation energies, ionization potentials,
and C-S and S-H bond energies. The calculations are compared to both e
xperiment and other calculations for this system. The computations ass
ist in the interpretation of CH3SH photodissociation dynamics observed
by Butler and co-workers.