Dance of HMX molecule in conformational space by quasi-static heating: a combined Raman spectroscopy and theoretical study

ORAL

Abstract

The complexity of HMX polymorphs arises from conformers and molecular packing. In this study, HMX single crystal is heated at rates of 0.1 or 0.2 K/min during phase transitions. The sample is equilibrated at least 15 minutes at every step of increasing temperature to achieve the quasi-static condition. Raman spectroscopy is performed to monitor transitions between conformers by fitting position and full width at half maximum of the observed spectra. Conformers, transition states and IRC are verified at the level of DLPNO-CCSD(T)/cc-pVQZ//M062X-D3(0)/def2-TZVP for single HMX molecule. We attribute the response of spectra to ring puckering and nitro vibrations during phase transitions by analyzing Raman spectra and decomposition and identification of vibrational modes. Our results provide evidence of β-α and subsequent α-δ phase transition, which agree with recent thermodynamic model that α-HMX must be thermodynamically stable in phase diagram.

*This work was financially supported by the Science Challenge Project (Grant TZ2016001)

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Presenters

  • Yangyang Zeng

    • National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics

Authors

  • Yangyang Zeng

    • National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics

  • Chan Gao

    • Department of Physics, University of Science and Technology of China

  • guoyang yu

    • National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics

  • Rucheng Dai

    • The Centre for Physical Experiments, University of Science and Technology of China

  • Zhongping Wang

    • The Centre for Physical Experiments, University of Science and Technology of China

  • Zengming Zhang

    • Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, School of Physical Sciences, University of Science and Technology of China
    • University of Science and Technology of China

  • Xianxu Zheng

    • National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics

  • YanQiang Yang

    • National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics