Thermodynamics of solid polymerized nitrogen

Polymeric cubic gauche phase of solid nitrogen, like other covalent structures, may exhibit both negative thermal expansion and essential deviations from the Dulong Petit law. We present a new extensive set of Monte Carlo data covering the region of negative heat expansion and both negative and positive deviations from the Dulong Petit law. A new model of solid polymerized nitrogen is proposed. It combines the modified Mie-Grüneisen model and anharmonic corrections to free energy of solid. A few parameters of the model are found on the basis of comparison with MC computer simulation data. The proposed model may be extended on other covalent solids.