Anharmonic lattice vibrations in solid N₂

Abstract

Anharmonic lattice vibration in solid γ-N₂ has been studied in terms of a Green's function perturbation method. The crystal hamiltonian is made up of a 12–6 atom-atom potential. Phonon band shapes of external lattice vibrations at q = 0 have been computed at several temperatures up to 40 K at a constant molar volume of 24·09 cm³. It is found that the calculated band maximum frequencies of Raman-active modes, E_g and B _1g , decrease with increasing temperature, which is consistent with experiment, while the frequencies of the other modes increase. The temperature dependence of the relative intensity, I(E_g )/I(B _1g ), is compared with experiment.