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We applied the Mayer group expansion method for solids to predict locations of the polymorphic phase transitions lines between molecular ɛ and ζ phases, as well as between molecular ζ phase and polymeric cubic-gauche-phase in highly compressed nitrogen solid. A simple potential model is proposed and its parameters are determined using known ab initio energy calculations for the molecular α phase. The results are compared with existing experimental data and the influence of intermolecular correlations on the temperature dependence of phase transition pressures is estimated. [ABSTRACT FROM AUTHOR]

The Mayer group expansion for solids proposed earlier is applied in prediction of the location of polymorphic phase transition line between the cubic and layered phases of polymeric nitrogen. The comparison with existing measurements revealed that theoretical calculations based on the proposed potential model calibrated on ab initio energy calculations are in agreement with existing experimental data. Predicted location of the polymorphic transition line and specific behavior of thermal properties of both phases in a wide temperature range is discussed. [ABSTRACT FROM AUTHOR]