Calculation of the Raman and IR frequencies from the volume data at high pressures in N2

Raman and IR frequencies of N2 in the molecular state are calculated as a function of pressure up to 160 GPa by using the volume data from the literature through the mode Grüneisen parameter. By determining the Grüneisen parameters for the lattice modes and vibrons which decrease mostly with increasing pressure from the observed frequency (Raman, IR) and volume data, the Raman and IR frequencies of those modes are calculated at various pressure at room and low temperatures. We find that the Raman and IR frequencies increase as the pressure increases in N2 as observed experimentally. This method of calculating the Raman and IR frequencies from the volume data can be applied to the some other molecular crystals.