Calculation of the inverse relaxation time and the activation energy as a function of temperature for the Raman modes close to the phase transitions in solid nitrogen

Abstract

The inverse relaxation time is calculated as a function of temperature for the transitions of alpha - beta (P = 0) and epsilon-delta(loc)-delta (at constant pressures) in the solid N-2. For this calculation, the observed data from the literature are used for the Raman frequency shifts and linewidths (FWHM) of the librational E-g mode (alpha - beta) and the internal modes of v(1) and v(2) (epsilon-delta(loc)-delta) in the nitrogen. From the temperature dependence of the inverse relaxation time, the activation energy is extracted for the Raman modes (E-g, v(r) and v(2)) to explain the order-disorder transitions (alpha - beta and epsilon-delta(loc)-delta) in this molecular solid. Close to the phase transitions, a power-law formula is suggested for the relaxation time in relation to the frequency shifts and linewidths, which can be applied to the molecular solids. (C) 2020 Elsevier B.V. All rights reserved.