Calculation of the thermodynamic functions from the Raman frequency shifts close to the 𝜀–δloc–δ transitions and Pippard relations in nitrogen

Abstract

Thermodynamic functions of the thermal expansion [Formula: see text], isothermal compressibility [Formula: see text] and the difference in the heat capacity [Formula: see text] are calculated as a function of temperature ([Formula: see text] GPa) close to the transitions of [Formula: see text][Formula: see text]–[Formula: see text][Formula: see text] and [Formula: see text][Formula: see text]–[Formula: see text][Formula: see text] in the solid nitrogen. This calculation is performed by using the observed Raman frequency shifts of vibrons [Formula: see text] and [Formula: see text]. Also, by using the observed [Formula: see text]–[Formula: see text] data, those thermodynamic functions are predicted at various pressures for the fluid–solid transition in nitrogen. For both calculations, observed data are used from the literature. From the temperature and pressure dependences of the thermodynamic functions studied, the Pippard relations are examined close to the [Formula: see text][Formula: see text]–[Formula: see text][Formula: see text][Formula: see text]–[Formula: see text][Formula: see text] transitions and also fluid–solid transition in nitrogen.We find that the thermodynamic functions can be predicted from the Raman frequency shifts and that the Pippard relations can be established for both the [Formula: see text][Formula: see text]–[Formula: see text][Formula: see text][Formula: see text]–[Formula: see text][Formula: see text] and fluid–solid transitions in nitrogen. This method of predicting the thermodynamic functions can also be applied to some other molecular solids.