We investigate the Hugoniot curve, shock-particle velocity relations, and Chapman-Jouguet conditions of the hot dense system through molecular dynamics （MD） simulations. The detailed pathways from crystal nitrometha...We investigate the Hugoniot curve, shock-particle velocity relations, and Chapman-Jouguet conditions of the hot dense system through molecular dynamics （MD） simulations. The detailed pathways from crystal nitromethane to reacted state by shock compression are simulated. The phase transition of N2 and CO mixture is found at about 10 GPa, and the main reason is that the dissociation of the C-O bond and the formation of C-C bond start at 10.0-11.0 GPa. The unreacted state simulations of nitromethane are consistent with shock Hugoniot data. The complete pathway from unreacted to reacted state is discussed. Through chemical species analysis, we find that the C-N bond breaking is the main event of the shock-induced nitromethane decomposition.展开更多
基于反应力场(reactive force field,ReaxFF)的反应分子动力学模拟的结果分析具有挑战性。国际首个ReaxFF MD化学反应分析及可视化工具VARxMD(visulization and analysis of ReaxFF molecular dynamics)可自动生成不同时刻之间完整的化...基于反应力场(reactive force field,ReaxFF)的反应分子动力学模拟的结果分析具有挑战性。国际首个ReaxFF MD化学反应分析及可视化工具VARxMD(visulization and analysis of ReaxFF molecular dynamics)可自动生成不同时刻之间完整的化学反应列表,通过物种检索进一步对反应路径进行分类。但VARxMD目前的反应分析针对的是某一确定条件下单一的ReaxFF MD模拟轨迹,利用VARxMD分析获得一次模拟的完整反应列表需要消耗大量计算资源和时间。本文提出基于数据库来储存VARxMD反应分析结果数据,基于数据库检索进一步分析反应的思路,并采用MVVM(model-view-view model)的系统设计模式、结合渐进式框架Vue.js建立了ReaxFF MD模拟的化学反应数据系统ReaxMDDB(reaction database of ReaxFF MD simulation)。系统应用于多个RP-3模型热解和氧化模拟反应数据的结果表明:该系统不仅实现了多个ReaxFF MD模拟的详细反应的统一分析和化学反应的2D分子结构显示,而且可永久保存模拟获得的反应数据集以备后续进一步分析反应机理。ReaxMDDB具有很好的通用性,为认识不同反应模拟所揭示的共性化学反应机理提供了方便的平台。展开更多
Understanding of metal oxidation is very critical to corrosion control,catalysis synthesis,and advanced materials engineering.Metal oxidation is a very complex phenomenon,with many different processes which are couple...Understanding of metal oxidation is very critical to corrosion control,catalysis synthesis,and advanced materials engineering.Metal oxidation is a very complex phenomenon,with many different processes which are coupled and involved from the onset of reaction.In this work,the initial stage of oxidation on titanium surface was investigated in atomic scale by molecular dynamics(MD)simulations using a reactive force field(ReaxFF).We show that oxygen transport is the dominant process during the initial oxidation.Our simulation also demonstrate that a compressive stress was generated in the oxide layer which blocked the oxygen transport perpendicular to the Titanium(0001)surface and further prevented oxidation in the deeper layers.The mechanism of initial oxidation observed in this work can be also applicable to other self-limiting oxidation.展开更多
反应分子动力学(Reaction Force Field Molecular Dynamics,ReaxFF MD)模拟通过在键级描述化学反应过程中键的断裂和形成,从微观尺度探索复杂的反应机理,弥补了实验研究的不足。该方法已广泛应用于油气地球化学领域,例如干酪根的生烃演...反应分子动力学(Reaction Force Field Molecular Dynamics,ReaxFF MD)模拟通过在键级描述化学反应过程中键的断裂和形成,从微观尺度探索复杂的反应机理,弥补了实验研究的不足。该方法已广泛应用于油气地球化学领域,例如干酪根的生烃演化、原油的裂解和相态演化等。本文系统总结和评述了原油裂解反应动力学分子模拟的现状、进展以及未来的发展趋势。首先,对原油各组分的裂解动力学特征、裂解过程、产物分布、生成途径以及热解初始反应机理方面取得的成果进行了总结,并分析了该领域目前存在的挑战及未来的发展方向。尽管分子模拟是研究原油裂解机理的有力工具,但目前仍处于初步研究阶段。现有的研究多采用原油中的某单一组分作为代表,并侧重于考查温度对原油裂解的影响,而对各组分间的相互作用、压力、介质条件和储层环境的影响研究尚不充分。未来的研究应聚焦于构建复杂真实的原油模型,还原地质条件下的原油裂解过程,并将分子模拟、实验和地质研究相结合,为系统研究油气的裂解机理提供重要参考和有用指导。当前的分子模拟研究表明,原油各组分的裂解动力学、裂解产物和裂解过程与实验结果基本一致。与此同时,分子模拟能够追踪自由基、过渡态以及中间体结构,并获取成键特征、活化能、选择性等重要信息。因此,分子模拟可以准确刻画各类烃分子的初始反应路径,并解释裂解产物的差异性。展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11374217)the Shandong Provincial Natural Science Foundation,China(Grant No.ZR2014BQ008)
文摘We investigate the Hugoniot curve, shock-particle velocity relations, and Chapman-Jouguet conditions of the hot dense system through molecular dynamics （MD） simulations. The detailed pathways from crystal nitromethane to reacted state by shock compression are simulated. The phase transition of N2 and CO mixture is found at about 10 GPa, and the main reason is that the dissociation of the C-O bond and the formation of C-C bond start at 10.0-11.0 GPa. The unreacted state simulations of nitromethane are consistent with shock Hugoniot data. The complete pathway from unreacted to reacted state is discussed. Through chemical species analysis, we find that the C-N bond breaking is the main event of the shock-induced nitromethane decomposition.
文摘基于反应力场(reactive force field,ReaxFF)的反应分子动力学模拟的结果分析具有挑战性。国际首个ReaxFF MD化学反应分析及可视化工具VARxMD(visulization and analysis of ReaxFF molecular dynamics)可自动生成不同时刻之间完整的化学反应列表,通过物种检索进一步对反应路径进行分类。但VARxMD目前的反应分析针对的是某一确定条件下单一的ReaxFF MD模拟轨迹,利用VARxMD分析获得一次模拟的完整反应列表需要消耗大量计算资源和时间。本文提出基于数据库来储存VARxMD反应分析结果数据,基于数据库检索进一步分析反应的思路,并采用MVVM(model-view-view model)的系统设计模式、结合渐进式框架Vue.js建立了ReaxFF MD模拟的化学反应数据系统ReaxMDDB(reaction database of ReaxFF MD simulation)。系统应用于多个RP-3模型热解和氧化模拟反应数据的结果表明:该系统不仅实现了多个ReaxFF MD模拟的详细反应的统一分析和化学反应的2D分子结构显示,而且可永久保存模拟获得的反应数据集以备后续进一步分析反应机理。ReaxMDDB具有很好的通用性,为认识不同反应模拟所揭示的共性化学反应机理提供了方便的平台。
基金Support of this work from the National Natural Science Foundation of China(Grant No.51361009)Work at Ames Laboratory was supported by the US Department of Energy,Basic Energy Sciences,Division of Materials Science and Engineering under Contract No.DE-AC02-07CH11358,including a grant of computer time at the National Energy Research Scientific Computing Centre(NERSC)in Berkeley,CA.
文摘Understanding of metal oxidation is very critical to corrosion control,catalysis synthesis,and advanced materials engineering.Metal oxidation is a very complex phenomenon,with many different processes which are coupled and involved from the onset of reaction.In this work,the initial stage of oxidation on titanium surface was investigated in atomic scale by molecular dynamics(MD)simulations using a reactive force field(ReaxFF).We show that oxygen transport is the dominant process during the initial oxidation.Our simulation also demonstrate that a compressive stress was generated in the oxide layer which blocked the oxygen transport perpendicular to the Titanium(0001)surface and further prevented oxidation in the deeper layers.The mechanism of initial oxidation observed in this work can be also applicable to other self-limiting oxidation.
文摘反应分子动力学(Reaction Force Field Molecular Dynamics,ReaxFF MD)模拟通过在键级描述化学反应过程中键的断裂和形成,从微观尺度探索复杂的反应机理,弥补了实验研究的不足。该方法已广泛应用于油气地球化学领域,例如干酪根的生烃演化、原油的裂解和相态演化等。本文系统总结和评述了原油裂解反应动力学分子模拟的现状、进展以及未来的发展趋势。首先,对原油各组分的裂解动力学特征、裂解过程、产物分布、生成途径以及热解初始反应机理方面取得的成果进行了总结,并分析了该领域目前存在的挑战及未来的发展方向。尽管分子模拟是研究原油裂解机理的有力工具,但目前仍处于初步研究阶段。现有的研究多采用原油中的某单一组分作为代表,并侧重于考查温度对原油裂解的影响,而对各组分间的相互作用、压力、介质条件和储层环境的影响研究尚不充分。未来的研究应聚焦于构建复杂真实的原油模型,还原地质条件下的原油裂解过程,并将分子模拟、实验和地质研究相结合,为系统研究油气的裂解机理提供重要参考和有用指导。当前的分子模拟研究表明,原油各组分的裂解动力学、裂解产物和裂解过程与实验结果基本一致。与此同时,分子模拟能够追踪自由基、过渡态以及中间体结构,并获取成键特征、活化能、选择性等重要信息。因此,分子模拟可以准确刻画各类烃分子的初始反应路径,并解释裂解产物的差异性。
