Tensors of thermal deformation for various polymorphic modifications of 2,4-dinitroanisole

Abstract

The anisotropic characteristics of thermal deformation of ultrapure 2,4-dinitroanisole (2,4-DNAN) crystals were determined by the methods of powder thermorentgenography of the internal standard. The points of structural changes are registered in increments of 10 K, and in the melting region of 2 and 1 K. Calculations of powder X-ray diffraction data are performed by methods of full-profile analysis with a cycle of quantum modeling of the structure of molecules integrated into the algorithm. The Pauli, Le Bail (WPPD), Rietveld (WPPF) and WPPM methods were used as reference methods for full-profile analysis. The main crystallographic axes and characteristic surfaces of the thermal deformation tensor α and β-2,4-DNAN are determined. At atmospheric pressure, the main coefficients of linear (α) and volumetric (β) thermal deformation (expansion) were at 293 K for α-2,4-DNAN with α₁(293) = 11,516 × 10⁻⁵ K⁻¹, α₂(293) = −0,120 × 10⁻⁵ K⁻¹, α₃(293) = 5,098 × 10⁻⁵ K⁻¹, β(293) = 16,333 × 10⁻⁵ K⁻¹; at 293 K for β-2,4-DNAN with α₁(293) = 13,217 × 10⁻⁵ K⁻¹, α₂(293) = 0,494 × 10⁻⁵ K⁻¹, α₃(293) = −8,6504 × 10⁻⁵ K⁻¹, β(293) = 6,8191 × 10⁻⁵ K⁻¹; at 260 K for β′-2,4-DNAN with α₁(260) = 25,214 × 10⁻⁵ K⁻¹, α₂(260) = −5,823 × 10⁻⁵ K⁻¹, α₃(260) = 7,741 × 10⁻⁵ K⁻¹, β(260) = 27,112 × 10⁻⁵ K⁻¹.