Thermal deformation and polymorphic transitions of 1,1-diamino-2,2-dinitroethylene in the temperature range from 145 to 475 K

Under atmospheric pressure conditions, direct polymorphic transitions α to β, β to γ and reverse γ to α were studied, as well as certain phase equilibrium points for 1,1-diamino-2,2-dinitroethylene (DADNE) were determined in the temperature range from 145 to 475 K. The anisotropic characteristics of the thermal deformation of DADNE crystals are determined by powder thermal x-ray diffraction of an internal standard. The points of structural changes were recorded in increments of 20, 10, and 2 K. The calculations of x-ray powder diffraction data were carried out using full-profile analysis methods with the integrated cycle of molecular modeling of the structure of molecules integrated into the algorithm.