The energy parameters of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane polymorphs and their phase transitions

Abstract

The calculated dispersion and electrostatic intermolecular interaction energies in crystals of γ, α(H2O), and ɛ polymorphs of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazawurtzitane (HNIW) were compared. Preliminarily, nonempirical quantum-chemical calculations of the three compounds with complete geometry optimization were performed using the GAUSSIAN-03 package and density functional theory. The dispersion intermolecular interaction energy was calculated with the “6-exp” potential. The van der Waals and dipole-dipole interaction energies were substantially different in crystals of different HNIW polymorphs, but total energy changes in phase transitions were close to zero. The calculated ɛ > γ and α(H2O) > γ phase transition energies were close to the experimental values determined using a differential calorimeter. Dehydration substantially influenced the kinetics and heat effects of polymorphic transitions.