Thermal strain tensors for benzotrifuroxane and pentaerythritol tetranitrate molecular crystals

In this paper, we present the thermal strain tensors for two energetic materials: pentaerythritol tetranitrate (PETN) and benzotrifuroxane (BTF). These tensors are calculated from the data of the x-ray polycrystal diffraction in the range of temperatures from 150 to 370 K for PETN and from 150 to 450 K for BTF. Points of structural changes in energetic materials are recorded in increments of 10 K. The x-ray diffractometry data were calculated using the Rietveld method with the molecular structure quantum simulation cycle being integrated into the computation algorithm. Principle crystallographic axes and characteristic surfaces of the thermal strain tensor were determined. Thermal strain tensors and their temperature dependence are given numerically, algebraically, and graphically. The obtained results can be used to derive equations of state of condensed BTF and PETN, and also to calibrate ab-initio models. (paper)