THE INFRARED-SPECTRUM OF TRIMETHYLENEMETHANE - PREDICTIONS OF INPLANE VIBRATIONAL FREQUENCIES FROM CORRELATED WAVE-FUNCTIONS

The infrared vibrational spectrum of trimethylenemethane (TMM) is predicted with self-consistent field and configuration interaction methods. The 3A′2 electronic ground state of TMM is described in terms of restricted Hartree-Fock theory and in light of experimental evidence. Analytic gradient methods are employed to optimize theoretical geometries for 3A′2 TMM; Vibrational frequencies are evaluated via analytic second-derivative techniques (self-consistent-field) and finite differences of analytic gradients (configuration interaction). The resulting IR-spectral predictions are modified to reflect average errors statistically associated with the two theoretical methods. © 1990 American Institute of Physics.