Raman Optical Activity spectra: basis set and electron correlation effects.

Raman and vibrational Raman Optical Activity (ROA) spectra have been calculated for three molecules: H$_2$O$_2$, CHDTF and CHDTOH. The effects of electron correlation on the ROA parameters of these relatively small systems have been investigated by means of the multiconfigurational self consistent field approach. A range of correlation-consistent basis sets has been used in the calculations. The basis set convergence of the calculated ROA parameters is fairly well achieved when sets of at least d-aug-cc-pVTZ quality are used. On the other hand, the aug-cc-pVDZ set seems to be sufficient for a qualitative analysis. Diffuse functions, possibly a double set, are essential to ensure a good quality of the calculated ROA spectrum. In most cases the sign and approximate magnitude of the ROA is correctly predicted at SCF level, and the corresponding ROA spectra should be considered qualitatively accurate.