QTAIM charge-charge flux-dipole flux models for the infrared fundamental intensities of difluoro-and dichloroethylenes

A quantum theory of atoms in molecules (QTAIM) charge−charge flux−dipole flux (CCFDF) decomposition of the MP2/6-311++G(3d,3p) level molecular dipole moment derivatives is reported for the cis-, trans-, and 1,1-difluoroethylenes and the cis- and trans-dichloroethylenes. Although the dipole moment derivatives and infrared fundamental intensities calculated at the MP2 level are overestimated for high-intensity bands corresponding to CF and CC stretching vibrations, the overall agreement is good with a root-mean-square (rms) error of 19.6 km mol-1 for intensities ranging from 0 to 217.7 km mol-1. The intensities calculated from the QTAIM/CCFDF model parameters are in excellent agreement with those calculated directly by the MP2/6-311++G(3d,3p) approach with only a 1.8 km mol-1 rms error. A high negative correlation (r = −0.91) is found between the charge flux and dipole flux contributions to the dipole moment derivatives. Characteristic values of charge, charge flux, and dipole flux contributions are found f...