缺陷微结构对CL-20热致相变影响的机理研究

含能材料是武器系统的关键材料，其核心为含能晶体。含能晶体的稳定性是确保武器系统稳定、安全与可靠的基础。但是，由于含能分子构型的多样性以及较弱的分子间作用力，使得含能晶体普遍存在多晶型与晶型转变现象，且缺陷常常会导致这一转变加剧；目前这一现象的微观机制的认知仍不清楚。本项目拟以目前应用能量最高的含能材料CL-20为对象，采用量子化学、分子动力学以及metadynamics等计算模拟方法对CL-20热致相变行为展开研究，重点研究位错、孔洞、溶剂包藏物缺陷微结构对热致相变的影响。探索CL-20固-固热致相变机理，通过分析相变过程中CL-20分子构象与取向变化、自由能的变化、多种相互作用的变化以及缺陷结构的演化等，获得缺陷微结构对CL-20热致相变的影响规律。本研究不仅有助于深入理解炸药晶体多晶型相变的物理本质，还可以为发展高能炸药相变抑制方法提供理论支撑，助力推进CL-20等含能材材料的应用。

Energetic materials are a class of key materials in weapon systems, of which the core is energetic crystals. The stability of energetic crystals is a foundation to guarantee the stability, safety and reliability of weapon systems. However, polymorphism and polymorphic transformation (PT) exhibit generally for energetic crystals, due to the high variability of molecular conformations and the weak intermolecular interactions. In addition, the polymorphic transformation can be accelerated by defects. Currently, the micro-mechanism of the polymorphic transformation of energetic materials remains still unclear. In this project, we will carry out a systematic study on the influence mechanism of dislocations, holes and solvent inclusions on the PT of CL-20, by combining ab initio calculations, molecular dynamics simulations and metadynamics method. Thereby, the configuration transformation and molecular orientation, free energy, molecular interactions, and evolution of defect structures will be analyzed, and the micro-mechanism of solid-solid phase transition of CL-20 and the influence of the defects on the mechanism will be clarified. Our result is expected to facilitate to understand the physical essence of the PT, present an important theoretical support for a PT control technique of energetic crystals, and promote the applications of CL-20 and other energetic materials.