Page 202 - Strategies and Applications in Quantum Chemistry From Molecular Astrophysics to Molecular Engineer

HARTREE-FOCK MODEL TO THE LOWEST SINGLET AND TRIPLET EXCITED STATES 185

3.3. TRANS-BIACETYL MOLECULE
In order to test the HPHF model with a larger system, we have considered the trans-
biacetyl molecule, which contains six atoms of the second row and six hydrogen atoms.
The energy values of the two extremal configurations for the double rotation of the
methyl groups were determined on the potential energy surface, with full geometry
optimization except for the molecular frame which is constrained to be planar. In
the same calculation, the barrier height was determined.