DENSITY-FUNCTIONAL THEORY STUDY OF VIBRATIONAL-SPECTRA .3. ASSIGNMENTOF FUNDAMENTAL VIBRATIONAL-MODES OF QUADRICYCLANE

Density functional theory BLYP (Becke's exchange and Lee-Yang-Parr' a correlation functionals), ab initio Hartree-Fock (HF) and hybrid DFT/H F B3LYP calculations were carried out to study the structure and vibra tional spectra of quadricyclane. The BLYP/6-31G and scaled HF/6-31G* frequencies correspond well with each other and with available experim ental assignment of the fundamental vibrational modes. Based on confor mity between the calculated and experimental results, a plausible assi gnment of two remaining a(1) modes and all non-CH stretching a(2), b(1 ), and b(2) modes is proposed.