Numerical techniques for the evaluation of non-adiabatic interactions and the generation of quasi-diabatic potential energy surfaces using configuration interaction methods

2000 ◽  
Vol 98 (21) ◽  
pp. 1677-1690 ◽  
Author(s):  
Alexander O. Mitrushenkov, Paolo Palmieri, Cr
Keyword(s):  
Potential Energy ◽  
Configuration Interaction ◽  
Potential Energy Surfaces ◽  
Numerical Techniques ◽  
Energy Surfaces

Features of the thioformaldehyde potential energy surfaces

1985 ◽  
Vol 63 (7) ◽  
pp. 1910-1917 ◽  
Author(s):  
John D. Goddard
Keyword(s):  
Potential Energy ◽  
Excited States ◽  
Configuration Interaction ◽  
Potential Energy Surfaces ◽  
Transition States ◽  
Basis Sets ◽  
Dissociation Limit ◽  
Molecular Dissociation ◽  
Energy Surfaces ◽  
Higher Excited States

The structures of seven minima and five transition states of the S0 and T1 potential energy surfaces of thioformaldehyde have been located at the 3-21G* SCF level. Further calculations have been carried out to determine harmonic vibrational frequencies and to examine the effects of larger basis sets and of configuration interaction on energy differences. The molecular dissociation limit of H2 and CS is thermodynamically accessible at the energy of the lowest n,π* excited states and the singlet thiohydroxymethylenes lie only slightly too high. However, there are large barriers of ~85 to 90 kcal mol−1 to the molecular dissociation or to the 1,2-hydrogen shifts from thioformaldehyde to the thiohydroxymethylenes. The dissociation to H and HCS requires ~85.4 kcal mol−1 on the ground singlet and faces a barrier of several kcal mol−1 relative to products on the triplet surface. Any unimolecular photochemistry of thioformaldehyde is likely to require excitation to higher excited states than the lowest n,π* states.

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