奥克托今（HMX）是常用高能炸药的主要含能组分。HMX具有多种相结构，在高温高压下会发生复杂的相变。不同相结构具有不同的晶体密度、感度和化学分解路径，直接影响到以HMX为基的高能炸药在外界刺激下的动态响应特性和爆轰性能。因此，有必要系统研究炸药的相变问题。然而现有实验技术对检测信号的解读并不充分，导致学术界对炸药相变过程微观物理机制的认识还很缺乏。严重制约了炸药相变理论体系的建立及其在实际中的应用。本项目拟采用从头算分子动力学（AIMD）结合TRAVIS动态光谱计算方法，研究HMX在不同温度、压力下的相结构变化和红外、拉曼光谱特性。探索晶体结构(化学键、分子构型、分子间作用等)与光谱信号(数量、位置、强度、形状)的对应关系。在此基础上，进一步解读已有实验光谱数据，从原子分子尺度研究炸药相变的物理机制。

Octogen (HMX) is the main energetic component of the commonly used high-explosive. HMX possesses several phase structures, which would complicatedly transform with each other under high temperature and pressure. The different phase structures of HMX have different crystal densities, sensitivities, and chemical decomposition pathways, directly affecting the dynamic response properties and detonation performance of the HMX-based high-explosive under external stimulation. Thus, it is necessary to systematically investigate the phase transition of explosive. However, the existing experimental techniques can not sufficiently interpret the detected signal, resulting in a lack of understanding of the microscopic physical mechanism of explosive phase transition. The establishment and application of the theory system of explosive phase transition are restricted. In this program, we will study the phase structure transformation and the features of Infrared, Raman spectra of HMX under different temperatures and pressures, basing on ab initio molecular dynamics (AIMD) combined with TRAVIS dynamic spectrum calculation method. The corresponding relationship between crystalline microscopic structures (chemical bonds, molecular configuration, intermolecular interaction, and so on) and spectrum signal (quantity, position, intensity, and shape) is explored. Basing on that, the existing experimental spectrum data is further analyzed to uncover the physical mechanism of explosive phase transition at atomic and molecular level.