Performance of RIJCOSX approximation and numerical differentiation in modeling of structure and spectra of 2-(2'-hydroxyphenyl)benzoxazole

Structure, vibrations, vertical transitions in the ground and first excited states of an isolated molecule of 2-(2'-hydroxyphenyl)benzoxazole by density functional theory and time-dependent density functional theory are calculated by DFT and TDDFT methods with conventional approach and RIJCOSX approximation. It is found that results obtained by the RIJCOSX approximation are close to those obtained by conventional approach for the properties in the ground state and vertical transitions. RIJCOSX approximation provides good correspondence of values for relative energies of the structures in the excited state. For calculated vibrations in the excited state the difference in frequency reaches 40 cm-1 and there are permutation of modes and difference in forms. Deviations in the calculated vibrational spectra related to the usage of numerical derivatives instead of analytical are considered for the molecule in the ground state.