Systematic Investigation of Modern Quantum Chemical Methods to Predict Electronic Circular Dichroism Spectra

Abstract

The ability of different quantum chemical methods to predict experimental electronic circular dichroism (CD) spectra is critically evaluated. Two single-reference, time-dependent approaches based either on density functional theory (TDDFT) or a simplified coupled-cluster expansion (CC2) and two multireference methods (MRMP2 and DFT/MRCI) are considered. The methods are applied to a test suite of seven molecules including a wide range of difficult chromophores (“real-life” examples) and to three model systemsH2S2, twisted ethylene, and dimethyloxiranewhere accurate ab initio MRCI reference data are used for comparison. To investigate the effect of “exact” exchange mixing systematically, the TDDFT calculations were carried out with the BP86, B3-LYP, and BH-LYP functionals. The time-dependent Hartree−Fock (TDHF) method was included as an “upper limit” for the HF-exchange part in the functional. In general, it is found that the accuracy of most of the simulated spectra (except those from TDHF) is good enough ...