Directly Insight Into the Inter- and Intramolecular Interactions of CL-20/TNT Energetic Cocrystal through the Theoretical Simulations of THz Spectroscopy
Directly Insight Into the Inter- and Intramolecular Interactions of CL-20/TNT Energetic Cocrystal through the Theoretical Simulations of THz Spectroscopy
复制标题
通过太赫兹光谱的理论模拟直接洞察CL-20/TNT高能共晶的分子间和分子内相互作用
DOI：
10.1021/acs.jpca.5b10782
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发表时间：
2016
影响因子：
2.9
通讯作者：
Pei Chong-Hua
中科院分区：
文献类型：
--
作者：
Shi Lu;Duan Xiao-Hui;Zhu Li-Guo;Liu Xun;Pei Chong-Hua
与共晶形成物相比，爆炸性共晶具有独特的堆积排列和复杂的分子间相互作用。识别爆炸共晶的光谱特征，利用太赫兹波段的光谱来理解分子的低频模式，对于明确共晶形成的机理具有重要价值。本文采用分子动力学（MD）模拟和固体密度泛函理论（DFT）计算相结合的方法，研究了CL-20/TNT共晶及其不同取向和共晶前体的太赫兹（THz）吸收光谱，确定了相应THz振动模式的系统和全面归属。不同晶向的共晶和共晶前体的THz光谱比较表明，CL-20/TNT共晶具有5个独特的低频吸收峰，其中0.25、0.73和0.87 THz是强的晶体振动，0.87 THz也是由C-H···O氢键弯曲振动引起的; 1.60和1.85 THz的特征来自C-H···O氢键伸缩振动。此外，CL-20/TNT共晶的（001）方向的THz光谱证实CL-20的分子构象与β-多晶型物中的分子构象相同，而不是原料ε-CL-20的初始构象。
Compared with cocrystal coformers, an explosive cocrystal has distinctive packing arrangements and complex intermolecular interactions. Identifying the spectral signatures of an explosive cocrystal and understanding the molecular low-frequency modes by means of the spectrum in the terahertz range are of great worth to the explicit mechanism of cocrystal formation. In this work, on the basis of the joint molecular dynamics (MD) simulations and solid-state density functional theory (DFT) calculations, we have investigated the terahertz (THz) absorption spectra of the CL-20/TNT cocrystal and its different directions as well as cocrystal coformers and determined the systematic and all-sided assignments of corresponding THz vibration modes. The THz spectral comparison of the cocrystal with different directions and the cocrystal coformers indicates that the CL-20/TNT cocrystal has five fresh low-frequency absorption features as unique and discernible peaks for identification, in which 0.25, 0.73, and 0.87 THz are attributed to intensive crystalline vibrations; 0.87 THz is also caused by C–H···O hydrogen-bonding bending vibrations; 1.60 and 1.85 THz features originate from C–H···O hydrogen-bond stretching vibrations. Additionally, the THz spectrum of the (001) direction of the CL-20/TNT cocrystal verifies that the molecular conformation of the CL-20 is the same as that in the β-polymorph, other than the initial conformation of raw material ε-CL-20.