Comparative analysis of calculation methods in electron spectroscopy

The possibilities of the electron density functional method DFT with hybrid functionals B3LYP and M06-HF with various basis sets for calculating the electronic spectra of molecules were analyzed. It was shown that the specific form of the basis sets 6-31G, cc-PVDZ, 6-311 $++$ G ** are not significantly influence on the value of the long-wave transition band in the electronic absorption spectrum of 3,6-diamino-N-methyl phthalimide. The choice of the hybrid potential in the method of the non-stationary theory of the TD-DFT density functional and especially using CIS configuration interaction scheme leads to noticeable differences in the calculated values of the ($\pi-\pi*$)-transition band. For all other transitions, the changes were not so significant. The electronic spectra of ten compounds — substituted phthalimide were calculated by different methods using the 6-31G basis set. The structure of a substance uniquely determines the spectrum pattern. Comparing results of calculations of these compounds by the TD-DFT method and the CIS method, which includes single-excited states, we concluded that the best agreement with the experiment is observed using the CIS method and the 6-31G basis set.