Electro-optical parameters for computation of nonresonance Raman scattering intensities of peptides
Résumé
A set of electro-optical parameters (EOPs) of cylindrical zero-order bond polarizability model (BPM) for chemical bonds found in peptides was obtained from the results of quantum-chemical computations. The calculation of the polarizability tensors and the Raman scattering activities of four test molecules (N-methylacetamide, N,N-dimethylacetamide, dialanine, and diglycine) has shown that the BPM calculated quantities are in good agreement with the reference data obtained in experiments or derived by quantum-chemical calculations. The mean molecular polarizabilities are reproduced with the maximum relative error of 1.6%. A good agreement was obtained for the Raman activity of stretching vibrations, whereas a limited performance of the EOPs was found for the vibrational modes with a significant contribution of the bending internal coordinates involving H atoms. The origins of the discrepancies are analyzed, and the ways of improvement of the model performance are discussed.