The theoretical calculations of vibrational spectra of guanidine selenate and guanidinium sulphate. Determination of direction of transition dipole moments by two methods: oriented gas model and changes in displacement eigenvectors computed by DFT method

Abstract

For guanidinium selenate and guanidinium sulphate the energy was minimized and the theoretical vibrational frequencies and potential energy distribution (PED) were calculated by density functional method. The 6-31++G(d,p) basis set was used. The assignment of the bands has been made on the basis of the calculated PED. For calculated equilibrium geometries two methods for determination of direction of transition dipole moments (TDM) were used. The oriented gas model was used for calculation of ‘static’ TDM and from the other side the ‘dynamic’ approximation of TDM by analysis of changes in internal coordination during characteristic vibrations was performed.