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A theoretical study of rotational profiles of molecular absorption bands is essential for direct comparison with observations of diffuse interstellar bands. Applications using gaussian quantum-chemical approach within DFT are presented. Structural and vibrational properties of the polycyclic aromatic hydrocarbon ovalene cation (C32H14+) are obtained. We discuss the expected profile of the first electronic transition of such molecule, obtained with a Monte Carlo model of its rotation in the physical conditions of low temperatures and absence of collisions which are characteristic of the interstellar medium (ISM).

Electronic ground-state properties and quasiparticle energies of the charge-transfer insulating oxides SrO and MgO have been computed. Structural properties calculations have been performed within DFT–LDA, while for the electronic excitations an efficient DFT–GW scheme, founded on the use of a model dielectric function, has been used. The comparison of our results with available theoretical and experimental data turns out to be satisfactory either for the ground state or for the excitation spectrum.

We present our ab initio calculation of linear optical properties in cubic (c-BN) and layered hexagonal BN (h-BN). Our results show a reasonable agreement with existent theoretical results and with measured data for the imaginary part of the dielectric function in the case of h-BN, while for c-BN discrepancies arise between theory and experiment. We discuss the possible reasons of this mismatch.