红外非线性光学晶体在激光制导、毒品稽查、激光医疗等领域具有重要的战略意义和经济价值。申报人所在团队近来发现的Pb17O8Cl18（POC）三元化合物，具有大的倍频效应（2.090μm，6倍AgGaS2）和高的激光损伤阈值（12.8倍AgGaS2），综合性能优异。受制于大尺寸、高质量POC晶体的生长，该材料还没有获得实际应用。本项目将从微观自发结晶机制出发，结合数值模拟，阐明POC熔体的自发结晶机理，揭示影响晶体生长的关键热力学与动力学参数，指导优化POC晶体熔体法生长的工艺，生长出厘米级高质量的POC单晶，用于评估POC光学器件在红外非线性光学领域的应用前景。通过对POC熔体在温场约束条件下自发结晶及生长动力学的研究，将有助于揭示同成分熔融化合物的自发结晶及生长机制，丰富和发展晶体学中复杂化合物晶体的成核生长理论，为同成分熔融化合物利用熔体法进行晶体的生长提供理论的指导。

Infrared Nonlinear Optical (IR NLO) crystals are widely used in laser guidance, drug inspection, laser medicine and so on, which have great strategic importance and economic values to a country. Pb17O8Cl18 (POC), a promising IR NLO material, has been developed by our team. POC shows a large second-harmonic generation response (2.090 μm, ~6.0 × AgGaS2), high laser damage thresholds (~12 × AgGaS2), as well as good comprehensive performances. However, due to the experimental challenge in crystal growth of large-size and high quality single crystal, POC hasn’t been used in laser technology yet. In the project, based on the experimental observation and theoretical simulation, we will study the mechanism of POC spontaneous crystallization from melt, uncover the crystal growth thermodynamics and kinetics, optimize the growth of POC crystal, and then grow high quality transparent POC single crystal with centimeter size，and evaluate the application prospect of POC optical device in IR NLO fields. The results will help to clarify the spontaneous crystallization mechanism of congruent melt compounds under cooling, enrich the crystal nucleation and growth theory, and provide new insights into the crystal growth of congruent melt compounds by melt methods.