DFT Functional Analysis for the Modeling Raman Bands and Absorption Spectra of the Lycopene Structure

The different length carotenoids have linear correlation between the Raman ν1band and S0-S2 absorption. The possible distortions in carotenoids due to dimer effects may change the correlation what can be modelled by using DFT methods. Thus, DFT functional must be suitable to predict good geometries, Raman and UV absorption (S0-S2) spectra. This should be true for the monomer and dimer structures.It is known that not all DFT functional are suitable for all this type calculation. We performed DFT functional analyses on the lycopene which represents typical carotenoid molecule. We have analyzed 281 different DFT functional. The analysis was based on the 4 type calculations: monomer geometry optimization, monomer Raman spectra, monomer excited states and H-dimerexcited state splitting at different distances. According results there wasn’t one particular functional which could be suitable for the all 4 different type calculations. In the paper we classified DFT functional which are the best for the geometry optimization, monomer Raman, monomerexited states and H-dimerexcited state splitting calculations.

Keywords: TD-DFT; Raman;DFT; lycopene; carotenoids.