On the Raman and infrared vibrational spectra of the ɛ and ζ phases of oxygen. Systematic DFT studies with localized basis sets

Abstract

We address the pressure evolution of the Raman and infrared vibrational modes of the ɛ and ζ phases of oxygen. We use DFT with various GGA and hybrid functionals with localized atomic basis sets. The frequency evolution of the OV, MIR, FIR, L1 and L2 modes is in good agreement with experimental data. The better performance of all methods at pressures >30GPa is related to the decreasing multireference character of the (O2)4 unit cell wavefunction. Hybrid functionals predict the ɛ–ζ phase transition by the appearance of red-shifted L1 and L2 Raman modes in the transition pressure region.