单轴压缩下固态硝基苯的第一性原理研究  

First-principle simulation of solid nitrobenzene under uniaxial compression

作　　者：范俊宇 郑朝阳[2] 苏艳[1] 赵纪军[1] Fan Jun-Yu Zheng Zhao-Yang Su Yan Zhao Ji-Jun(Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Ministry of Education, Dalian 116024, China National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China)

机构地区：[1]大连理工大学,三束材料改性教育部重点实验室,大连116024 [2]中国工程物理研究院流体物理研究所,冲击波与爆轰物理国家实验室,绵阳621900

出　　处：《物理学报》2017年第3期59-67,共9页Acta Physica Sinica

基　　金：国防基础科研核基础科学挑战计划(批准号:JCKY2016212A501);国家自然科学基金(批准号:11674046);中国博士后科学基金(批准号:2016M592704);大连理工大学超算中心资助的课题

摘　　要：采用第一性原理密度泛函理论结合经典色散修正方法,对固态硝基苯在单轴压缩下的基本结构关系进行了计算.静水压缩和单轴压缩都压缩到初始平衡体积的70%.将静水压下优化后的晶胞体积、晶格参数以及平衡条件下的晶格能与实验值进行了比较,均符合较好.同时,为了充分地表征固态硝基苯的各向异性,将硝基苯沿着三个晶格矢量的方向进行单轴压缩,把每个方向的应力张量、能带带隙、每个原子能量的改变分别作为体积压缩比的函数进行了比较和分析.其中,最显著的各向异性效应是在体积压缩比为0.76时,沿X轴压缩导致硝基苯能带带隙闭合,体系呈金属化;而静水压缩或沿Y轴和Z轴压缩时体系始终呈半导体状态,带隙均大于1.59 eV.为了充分理解这一各向异性特性,我们计算了硝基苯晶体的局域态密度和电荷密度分布,并对金属化现象做出了合理的分析和解释.在不同的压力加载条件下,通过对不同物理量的计算,发现X轴方向是硝基苯晶体内部最敏感的方向.这些各向异性效应的研究将有助于人们在原子尺度上深入理解固态硝基苯的物理化学性质.Energetic materials（EMs） including explosives, propellants and pyrotechnics have been widely used for the military and many other purposes. Solid nitrobenzene（an organic molecular crystal） could be considered as a prototype of energetic material. Up to now, numerous studies have been devoted to crystal structures, spectrum properties and decomposition mechanisms for solid nitrobenzene experimentally and theoretically. However there has been a lack of the comprehensive understanding of the anisotropic characteristics under different loading conditions. Thus we investigate the hydrostatic and uniaxial compressions along three different lattice directions to determine this anisotropic effect.In this work, the density functional theory calculations are performed based on Cambridge Sequential Total Energy Package（CASTEP） code using normconserving pseudo potentials and a kinetic energy cutoff of 700 e V. The generalized gradient approximation with the Perdew-Burke-Ernzerhof parameterization is used. Monkhorst-Pack k-point meshes with a density of 0.05 ？^（-1） are used for Brillouin-zone integration. The empirical dispersion correction by Grimme is taken to account for week intermolecular interactions. The hydrostatic compressions are applied from 0 GPa to 20 GPa. Cell volume, lattice shape and coordinates of the atoms could be fully relaxed. while uniaxial compression is applied up to 70% of the equilibrium cell volume in steps of 2% along their lattice directions respectively. At each compression step, only atomic coordinates are allowed to relax, with the lattice fixed. The equilibrium lattice structures under hydrostatic compressions are obtained by full relaxation at 0 K temperature. In ambient condition, the calculated volume and parameter of the unit cell are underestimated compared with the experimental data, and corresponding errors are -2.98%, 0.01%,-4.39%, 5.71% respectively. In contrast, the calculated lattice energy is overestimated compared with the range of experimental results with 5.71%

关 键 词：硝基苯 单轴压缩 静水压 含能材料 

分 类 号：TB34[一般工业技术—材料科学与工程]