Comparative quantum mechanical static and dynamic approaches to modelling vibrational spectra
Résumé
We present quantum mechanical (QM) vibrational computations beyond the harmonic approximation from an effective second order perturbative (VPT2), a variational (VCI) and a variation-perturbation (VCI-P) treatments - defined as static approaches- as well as vibrational analysis from DFT molecular dynamics trajectories at 300K and 600K. The four schemes are compared in terms of prediction of fundamental transitions, simulation of the corresponding medium infrared (MIR) spectrum at the same level of theory using the B3LYP/6-31+G(d,p) description of the electronic structure for the formamide that exhibits both torsional and double-well type modes. © 2009 American Institute of Physics.