TATB晶体声子谱及比热容的第一性原理研究  

First-principles study of the phonon spectrum and heat capacity of TATB crystal

作　　者：蒋文灿[1,2] 陈华[1] 张伟斌[1] 

机构地区：[1]中国工程物理研究院化工材料研究所,绵阳621900 [2]中国工程物理研究院研究生部,绵阳621900

出　　处：《物理学报》2016年第12期216-224,共9页Acta Physica Sinica

基　　金：中国工程物理研究院科学技术发展基金(批准号:2013A0302013)资助的课题~~

摘　　要：利用第一性原理并结合vd W-DF2范德瓦耳斯力校正研究了TATB(C6H6O6N6)晶体声子谱及比热容.采用冷冻声子法计算了TATB晶体声子谱和声子态密度,发现在2.3 THz附近TATB声子态密度最大,证实了太赫兹光谱实验观察到的2.22 THz附近的强吸收峰.基于声子态密度研究了振动模式对比热容的贡献,分析结果表明,常温下0—27.5 THz频段振动模式贡献了比热容的93.7%.同时比较了升温过程中振动模式对比热容的贡献,指出TATB热分解的引发键是C—NO_2键断裂的可能性更大.The widely used energetic material 1, 3, 5-triamino-2, 4, 6-trinitrobenzene （TATB） is an extremely powerful explosive and known for its extraordinary insensitivity to external stimuli （i.e., shock, friction, impact）. TATB crystal exhibits graphitic-like sheets with significant inter- and intra-molecular hydrogen bondings within each layer and weak van der Waals （vdW） interactions between layers. Although TATB has been extensively studied both theoretically and experimentally, a fully understanding of its unique detonation phenomenon at a microscopic level is still lacking. Before establishing the exact pathway through which the initial energy is transferred, a fundamental knowledge of both the lattice vibrations （phonons） and molecule internal vibrations must be gained at the first step. Recently, it has been demonstrated that density functional theory （DFT） is inadequate in treating conventional energetic materials, within which dispersion interactions appear to be major contributors to the binding forces. In the present work, phonon spectrum and specific heat of TATB crystal are calculated in the framework of DFT with vdW-DF2 correction, which has been validated in our previous studies of the equation of state, structure and vibration property of TATB crystal under pressures in a range of 0–8.5 GPa. Structure optimization is preformed at zero-pressure, followed by calculating the equation of state, crystal density and lattice energy. The computed results are found to fit well with the experimental and other theoretical values. Frozen phonon method is used to calculate the phonon spectrum and phonon density of states. We find that the phonon density of states reaches its maximum at a vibration frequency of 2.3 THz, which is in good agreement with the strong absorption peak at 2.22 THz observed by THz spectroscopy. The assignment of several Raman active vibrations of TATB above 7.5 THz is given, and a comparison with other published results is also made in this study. Furthermore, the contri

关 键 词：TATB 声子谱 比热容 范德瓦耳斯力校正 

分 类 号：O735[理学—晶体学]