ChemInform Abstract: Assignment of the Fundamental Frequencies of p-Benzoquinone: A Scaled Quantum Mechanical Force Field Study.

Abstract

The recently developed unrestricted Hartree-Fock natural orbital-complete active space (UNO-CAS) method is applied to the determination of the geometry and force field of p-benzoquinone. With an active space consisting of eight electrons distributed in eight π orbitals (8×8) and the 6-31G* basis set, UNO-CAS predicts CC and CO distances in good agreement with gas electron diffraction results. The full quadratic force field is obtained by an empirical scaling of the 8×8 UNo-CAS/4-21G force constants evaluated at the 6-31G* UNO-CAS geometry