I二甲醚在橡胶中扩散特性的分子动力学模拟摘要随着计算机的性能提高和计算技术的长足发展，利用计算机对物质的微观结构和运动进行数值模拟计算得到了迅速发展，并在此基础上发展了运用数值运算统计求和的方法:分子动力学法。本文通过分子动力学方法，应用Accelrys公司的软件MaterialsStudio来模拟二甲醚在不同橡胶中的扩散行为，用Einstein法和Green-kubo法求得二甲醚在6中橡胶不同温度下的扩散系数，并对两种算法进行比较。基于COMPASS力场进行建模。为了使模拟体系接近真实体系，模型的构建采用三维周期性边界条件，选取能量最低、体系最稳定的周期边界作为初始构型。然后对模拟体系进行能量优化和预平衡，进行NVT系综的分子动力学模拟以便得到二甲醚在橡胶内的扩散过程和运动轨迹，最后采用两种算法计算二甲醚在橡胶内的扩散系数通过本研究的计算数据，发现分别通过两种算法得到的二甲醚在橡胶中的扩散系数在数量级上保持一致，除去个别点外，两者的相对误差在一定稳定范围内。Green-Kubo法计算需要积分，较为繁琐，误差较大，Einstein法计算简便，计算结果与实验值比较接近。用Green-Kubo法求得二甲醚在343k温度下的氟橡胶中的模拟扩散系数最大，可推测此温度下在所有研究的橡胶中氟橡胶的耐二甲醚的能力最差。基于本文研究得到的数据，进行综合分析后认为本文所研究的橡胶中丙烯腈含量为20%的氢化丁腈橡胶的耐二甲醚性能最好。关键词：二甲醚，分子动力学，橡胶，扩散系数ABSTRACT┊┊┊┊┊┊┊┊┊┊┊┊┊装┊┊┊┊┊订┊┊┊┊┊线┊┊┊┊┊┊┊┊┊┊┊┊┊II二甲醚在橡胶中扩散特性的分子动力学模拟Withtherapiddevelopmentofcomputerperformanceandcomputingtechnology,theuseofcomputersandthemovementofmaterialmicrostructurenumericalsimulationhavebeendevelopingrapidly,andthedevelopmentofstatisticalsummationofnumericalcalculationmethodbasedonthis:MolecularDynamics.Inthearticle,useMaterialsStudioofAccelrysCompanytosimulationDMEdiffusionbehaviorinthedifferentrubber,andobtainthediffusioncoefficientofDMEin6typesofrubberthathasdifferenttemperaturebyusingEinsteinandGreen-kuboalgorithms,andcomparethetwoalgorithms.CreatemodelbasedontheCOMPASSforcefield.Inordertosimulatethesystemclosetotherealsystem,buildamodelofthree-dimensionalperiodicboundaryconditions,andselectthelowestenergy,themoststablesystemwithperiodicboundaryastheinitialconfiguration.Thenthesimulationsystemforenergyoptimizationandpre-equilibrium,moleculardynamicssimulationswithNVTensembleinordertogetDMEdiffusionprocessesandtrajectoriesintherubber,finally,calculateDMEdiffusioncoefficientintherubberwithtwoalgorithms.Afteranalyzingthedataofthisstudy,foundthattheDMEdiffusioncoefficientsintherubberwereobtainedbythetwoalgorithmsconsistentinmagnitude,exceptfromafewpoints,therelativeerrorofthetwoalgorithmswithinastablerange.Green-Kubomethodrequiresintegration,morecumbersome,errorislarge,Einsteinmethodissimple,andtheresultsareclosetotheexperimentalvalue.Underthe343k,simulationofDMEdiffusioncoefficientinfluorinerubberobtainedwithgreen-kubomethodisthebiggestoftheotherrubberinthestudy,itcanbespeculatedthattheabilityresistantingDMEoffluorinerubberistheworstoftheotherrubberintherubberunderthetemperature.Inthispaper,basedonthedataobtained,afteracomprehensiveanalysis，ithinkthattheabilityresistantingDMEofHNBR20isthebestoftheotherrubberstudiedinthispaper.KEYWORDS:Dimethylether,Moleculardynamics,Rubber，Diffusioncoefficient目录第一章绪论............................................................11.1分子模拟方法的分类...............................................11.1.1量子力学法.................................................11.1.2分子力学法..........
