Uniaxial compression behavior and spectroscopic properties of energetic 1,1-diamino-2,2-dinitroethylene (FOX-7) crystals from density functional theory calculations

Abstract

Using dispersion-corrected density functional theory (DFT), we investigate the effect of uniaxial compression on 1, 1-diamino-2, 2-dinitroethene (FOX-7) crystal. Principal and shear stresses along the [100], [010], and [001] orientations exhibit considerable anisotropic compressibility. Raman spectra are complemented by DFT calculations in vibrational modes. Several abnormal pressure-induced changes in selected Raman modes are observed along the [100] orientation. Combined Raman peak shifts with inter/intra-molecular hydrogen bonds and N−H/N−O covalent bonds, the results demonstrate that the spectroscopic variation are associated with the rearrangement of hydrogen-bonded networks of FOX-7 crystal. These findings imply a possible phase transformation or some minor changes in molecular conformation in the pressure regions under uniaxial compression.