Micro-defects in an energetic material is an important factor for the formation of“hot spots”and successive explosive detonation. However, an understanding of the micro-mechanism of forming “hot spots” is limited and the development and application of energetic materials are hindered due to the less knowledge of micro-defects inside the materials. In order to understand the characteristics of micro-defects and explore the basic mechanism of forming“hot spots”caused by defects, the effects of molecular vacancy defect on the geometrical structure, electronic structure and vibration char-acteristics of Hexogeon (RDX) energetic materials are studied using the first-principle method, and the basic formation mechanism of initial“hot spot”is discussed. The effects of molecular vacancy defect on the RDX geometrical structure, electronic band structure, electronic density of states and frontier molecular orbitals are analyzed using the periodic model, while the influences of molecular vacancy defect on the vibration characteristics of RDX systems are calculated using the cluster model. Infrared vibration spectra and vibration characteristics of the internal molecules at the same vibration frequency for the perfect and defective RDX systems are obtained. It is found that vacancy defect makes the N—N bond near the defect long, and the molecular structure loose; some degenerate energy levels in the conduction band present separation and the electronic density of states decreases;the bottom of the conduction band and the top of the valence band contributed by N-2p and O-2p orbitals shift to the Fermi surface, which reduces the energy band gap and increases the activity of system. At the same time, the calculations of the frontier molecular orbitals and the infrared vibration spectra show that the molecular defect makes the charge distributions of highest occupied moleculer orbital concentrated mainly in the molecule near the defect, and the C—H and N—N bond energies decrease. For the defective system, some molecules around vacancy have large vibration amplitude towards the vacancy direction. This will be likely to cause hole to collapse and realize the conversion of energy. These characteristics indicate that the presence of molecular vacancy defect causes the energy band gap to decrease, the structures of the molecules near the defect become loose, the charge distribution increases and the reaction activity augments. When the defective system is loaded by external energy, the molecules near the defect are expected to be unstable. The C—H or N—N bonds in those molecules are more prone to rupture to cause chemical reaction and release of energy, which is expected to be responsible for the forming of“hot spot”. These results provide some basic micro-information about revealing the formation mechanism of“hot spots”caused by molecular vacancy defects.%含能材料中的微观缺陷是导致“热点”形成并相继引发爆轰的重要因素。然而，由于目前人们对材料内部微观缺陷的认识不足，限制了对含能材料中“热点”形成微观机理的理解，进而阻碍了含能材料的发展和应用。为了洞悉含能材料内部微观缺陷特性及探索缺陷引发“热点”的形成机理，利用第一性原理方法研究了分子空位缺陷对环三亚甲基三硝胺(RDX)含能材料的几何结构、电子结构及振动特性的影响，探讨了微观缺陷对初始“热点”形成的基本机理。采用周期性模型分析了分子空位缺陷对RDX几何结构、电子能带结构、电子态密度及前线分子轨道的影响。采用团簇模型分析了分子空位缺陷对RDX振动特性的影响。结果发现，分子空位缺陷的存在使其附近的N—N键变长，分子结构变得松弛；使导带中很多简并的能级发生分离，电子态密度减小，并使由N-2p和O-2p轨道形成的导带底和价带顶均向费米面方向移动，降低了能带隙值，增加了体系活性。前线分子轨道及红外振动光谱的计算分析表明，分子缺陷使最高已占分子轨道电荷主要集中在缺陷附近的分子上，且分子中C—H键和N—N键能减弱。这些特性表明，分子空位缺陷的存在使体系能带隙变小，并使缺陷附近的分子结构松弛，电荷分布增多，反应活性增强；在外界能量激发下，缺陷附近分子将变得不稳定，分子中的C—H键或N—N键较易先发生断裂，发生化学反应释放能量，进而成为形成“热点”的根源。
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