中文摘要：

SⅡ型R134a制冷剂笼状水合物是理想的蓄冷介质之一。基于分子动力学（MD）方法，建立晶体结构模型，在NPT系综下运算，通过观察最终构象，分析计算体系中粒子的均方位移（MSD）和径向分布函数（RDF），从微观上揭示了小分子和温度对SⅡ型水合物晶体结构稳定性的影响。结果表明：小分子对小晶穴（5 12）占有率从0．25变化到1．00，占有率为0．25和0．50时，水合物晶体结构分解严重，体系中分子混乱，晶体结构难以稳定存在，占有率在0．75以上时，水合物晶体结构清晰有序，能够稳定存在；当体系温度由260K增大到290K时，水合物结构的稳定性逐渐降低，在280K时晶体结构出现扭曲变形，此时有部分水合物开始分解。

英文摘要：

R134a refrigerant SⅡ clathrate hydrate is an ideal medium for accumulation of cold. Based on the molecular dynamics （MD） method, a crystal structure model was built and operated under the NPT ensemble. By observing the final conformation, the mean square displacement（MSD） and radial distribution function （RDF） of particles in the system were analysed, the affect of small molecules and temperature on the stability of the hydrate crystalline structure was revealed from the microscopic mechanism. Results indicate that the occupancy ratio of the small molecule to small crystal cavity （ 512 ） varies from 0.25 to 1.00. When the occupancy ratio is 0.25 and O. 50, the hydrate crystal structure decomposes gravely and the molecules in the system move chaotically, so the crystal structure is unstable. If the occupancy ratio is above 0.75, the hydrate crystal structure is so clear and orderly, the structure exists steadily. The hydrate structure stability reduces gradually when the temperature increases from 260 K to 290 K , the crystal structure at 280K distorts and hydrate starts to decompose partially.