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Shock‐driven electron redistribution of triamino trinitrobenzene has been studied by time‐resolved Raman spectroscopy and first‐principle calculation. The variation trends of electron densities of CNO2 bonds, HNH bonds and intermolecular hydrogen bonds (inter‐HB) are respectively analyzed from the Raman peak shifts and the intensity changes under shock conditions. In addition, the pressure‐dependent effective bond order is calculated by density functional theory. By combining the experimental and computational results, it is deduced that electrons redistribute mainly through two paths under shock loading. In one path, the electrons transfer from the HNH, CNH2, NO bonds, and the intramolecular hydrogen bonds (intra‐HB) to the inter‐HB; and in the other path, the electrons transfer from the NO and CC bonds to the CNO2 bonds. These results suggest that this mechanism is reversible under relatively modest shock conditions and may change the strength orders of some chemical bonds and make some chemical bonds broken easily under violent shock conditions. [ABSTRACT FROM AUTHOR]

Hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) is a secondary high‐explosive material with thermal stability and high‐detonation velocity. It has been widely utilized for military and civilian purposes. Using systematic first‐principle calculations, we comprehensively explore structural, mechanical, electronic, and vibrational properties of α‐RDX modulated by pressure loading. The evolutions of structure, elastic modulus, and band gap are examined. A near‐linear pressure response and strong anisotropy are shown preliminarily. Further, pressure response and strong anisotropy are exhibited by Raman spectra analysis under hydrostatic and uniaxial compressions. Calculated Raman spectrum is well in accordance with experimental data at ambient conditions. Under uniaxial compression, the anisotropic vibration properties of α‐RDX in different lattice directions are presented. The discontinuity in b axis and red shift along c axis, which is related to the modification of the strength of noncovalent interactions, is highlighted. Our results exhibit the comprehensive pressure responses and anisotropy of α‐RDX on the atomic level. [ABSTRACT FROM AUTHOR]

Shock‐driven intramolecular electron redistribution (IER) of cyclotrimethylene trinitramine (RDX) is proposed, which will be helpful for understanding the initiation and safety mechanisms of RDX materials under shock compressions. Laser‐driven shock wave was performed to generate a dynamic pressure, and time‐resolved Raman spectroscopy was used to probe the shock wave response of RDX. First‐principle calculations were utilized to identify Raman modes and determine a pressure‐dependent electron density distribution in RDX molecules. Raman peaks of RDX have blue shifts under shock loadings, which are caused by IER. According to calculations, it can be confirmed that electrons transfer from C–H and N–O bonds to N–N bonds under shock loadings in IER. We suggest that shock‐driven IER will make some chemical bonds be broken more easily under shock conditions. Shock‐driven IER of RDX is investigated by time‐resolved Raman spectroscopy under laser‐driven shock wave. When the RDX molecule is impacted by a shock wave, the electrons will transfer from the C–H and the N–O bonds to the N–N bonds under shock loading, and this process will be reversible under relatively low pressure conditions. [ABSTRACT FROM AUTHOR]

Using dispersion corrected density functional theory, we have investigated the uniaxial compression effect on pentaerythritol tetranitrate (PETN) crystal, which is an secondary high explosive. The principal stresses and shear stresses along different orientations exhibit considerable anisotropy. The Raman spectroscopy is used to explore the pressure effects on the vibrational properties of PETN. Several features are observed in selected Raman vibrational modes along different orientations. Especially, compression along the [0 0 1] orientation induces some anomalous changes of some vibrational modes. Through analyzing intermolecular hydrogen bonds, vibrational mode assignments and variation of the corresponding peak positions of PETN crystal, we propose that the changes between 15.8 and 17.6 GPa may be associated with a phase transformation. This present study has shed light on the anisotropic impact sensitivity and phase change of PETN under compression at atomistic scale. [ABSTRACT FROM AUTHOR]