Examining the impact of harmonic correlation on vibrational frequencies calculated in localized coordinates.

摘要: Carefully choosing a set of optimized coordinates for performing vibrational frequency calculations can significantly reduce the anharmonic correlation energy from self-consistent field treatment molecular vibrations. However, moving away normal also introduces an additional source arising mode-coupling at harmonic level. The impact this new component is examined range molecules, and method proposed correcting resulting frequencies by adding full coupling connected pairs pseudoharmonic modes, termed (harmonic correlation). This approach found to lift degeneracies coordinate optimization provides better agreement with experimental benchmark than uncorrected theory without relying on traditional correlated methods.