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
Developing a widely-used reactive force field is meaningful to explore the fundamental reaction mechanism on gas-surface chemical reaction dynamics due to its very high computational efficiency. We here present a stud...Developing a widely-used reactive force field is meaningful to explore the fundamental reaction mechanism on gas-surface chemical reaction dynamics due to its very high computational efficiency. We here present a study of hydrogen and its deuterated molecules dissociation on Pd surfaces based on a full-dimensional potential energy surface （PES） constructed by using a simple second moment approximation reactive force field （SMA RFF）. Although the descriptions of the adsorbate-substrate interaction contain only the dissociation reaction of H2/Pd（111） system, a good transferability of SMA potential energy surface （PES） is shown to investigate the hydrogen dissociation on Pd（100）. Our simulation results show that, the dissociation probabilities of H2 and its deuterated molecules on Pd（111） and Pd（100） surfaces keep non-monotonous variations with respect to the incident energy Ei, which is in good agreement with the previous ab initio molecular dynamics. Furthermore, for the oriented molecules, the dissociation probabilities of the oriented H2 （D2 and T2） molecule have the same orientation dependence behavior as those oriented HD （HT and DT） molecules.展开更多
The reactive force field was used to study the molecular dynamics of cross-linked EPON 862 （diglycidyl ether of bisphenol-F） and DETDA （diethylene toluene diamine） system in order to predict its thermo-mechanical ...The reactive force field was used to study the molecular dynamics of cross-linked EPON 862 （diglycidyl ether of bisphenol-F） and DETDA （diethylene toluene diamine） system in order to predict its thermo-mechanical behavior under different loading conditions. The approach for building the EPON 862/DETDA structures, cross-linking, and equilibration of the systems, and the evaluation of the models are presented. The mechanical properties such as Young＇s and shear moduli, Poisson ratio, and yields strength as well as thermal properties such as glass transition temperature and coefficient of thermal expansion are predicted. The results are in close agreement with both experimental data and simulated results in literature.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
Biomass chemical looping gasification technology is one of the essential ways to utilize abundant biomass resources.At the same time,dimethyl carbonate can replace phosgene as an environmentfriendly organic material f...Biomass chemical looping gasification technology is one of the essential ways to utilize abundant biomass resources.At the same time,dimethyl carbonate can replace phosgene as an environmentfriendly organic material for the synthesis of polycarbonate.In this paper,a novel system coupling biomass chemical looping gasification with dimethyl carbonate synthesis with methanol as an intermediate is designed through microscopic mechanism analysis and process optimization.Firstly,reactive force field molecular dynamics simulation is performed to explore the reaction mechanism of biomass chemical looping gasification to determine the optimal gasification temperature range.Secondly,steady-state simulations of the process based on molecular dynamics simulation results are carried out to investigate the effects of temperature,steam to biomass ratio,and oxygen carrier to biomass ratio on the syngas yield and compositions.In addition,the main energy indicators of biomass chemical looping gasification process including lower heating value and cold gas efficiency are analyzed based on the above optimum parameters.Then,two synthesis stages are simulated and optimized with the following results obtained:the optimal temperature and pressure of methanol synthesis stage are 150℃ and 4 MPa;the optimal temperature and pressure of dimethyl carbonate synthesis stage are 140℃ and 0.3 MPa.Finally,the pre-separation-extraction-decantation process separates the mixture of dimethyl carbonate and methanol generated in the synthesis stage with 99.11%purity of dimethyl carbonate.Above results verify the feasibility of producing dimethyl carbonate from the perspective of multi-scale simulation and realize the multi-level utilization of biomass resources.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.
基金This work was supported by the National Natural Science Foundation of China （No.21506053） and Doctoral Scientific Research Foundation Project （KYY15023）.
文摘Developing a widely-used reactive force field is meaningful to explore the fundamental reaction mechanism on gas-surface chemical reaction dynamics due to its very high computational efficiency. We here present a study of hydrogen and its deuterated molecules dissociation on Pd surfaces based on a full-dimensional potential energy surface （PES） constructed by using a simple second moment approximation reactive force field （SMA RFF）. Although the descriptions of the adsorbate-substrate interaction contain only the dissociation reaction of H2/Pd（111） system, a good transferability of SMA potential energy surface （PES） is shown to investigate the hydrogen dissociation on Pd（100）. Our simulation results show that, the dissociation probabilities of H2 and its deuterated molecules on Pd（111） and Pd（100） surfaces keep non-monotonous variations with respect to the incident energy Ei, which is in good agreement with the previous ab initio molecular dynamics. Furthermore, for the oriented molecules, the dissociation probabilities of the oriented H2 （D2 and T2） molecule have the same orientation dependence behavior as those oriented HD （HT and DT） molecules.
文摘The reactive force field was used to study the molecular dynamics of cross-linked EPON 862 （diglycidyl ether of bisphenol-F） and DETDA （diethylene toluene diamine） system in order to predict its thermo-mechanical behavior under different loading conditions. The approach for building the EPON 862/DETDA structures, cross-linking, and equilibration of the systems, and the evaluation of the models are presented. The mechanical properties such as Young＇s and shear moduli, Poisson ratio, and yields strength as well as thermal properties such as glass transition temperature and coefficient of thermal expansion are predicted. The results are in close agreement with both experimental data and simulated results in literature.
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。
基金supported by the National Natural Science Foundation of China(22178189)the Natural Science Foundation of Shandong Province(ZR2021MB113)the Postdoctoral Science Foundation of China(2022M711746)。
文摘Biomass chemical looping gasification technology is one of the essential ways to utilize abundant biomass resources.At the same time,dimethyl carbonate can replace phosgene as an environmentfriendly organic material for the synthesis of polycarbonate.In this paper,a novel system coupling biomass chemical looping gasification with dimethyl carbonate synthesis with methanol as an intermediate is designed through microscopic mechanism analysis and process optimization.Firstly,reactive force field molecular dynamics simulation is performed to explore the reaction mechanism of biomass chemical looping gasification to determine the optimal gasification temperature range.Secondly,steady-state simulations of the process based on molecular dynamics simulation results are carried out to investigate the effects of temperature,steam to biomass ratio,and oxygen carrier to biomass ratio on the syngas yield and compositions.In addition,the main energy indicators of biomass chemical looping gasification process including lower heating value and cold gas efficiency are analyzed based on the above optimum parameters.Then,two synthesis stages are simulated and optimized with the following results obtained:the optimal temperature and pressure of methanol synthesis stage are 150℃ and 4 MPa;the optimal temperature and pressure of dimethyl carbonate synthesis stage are 140℃ and 0.3 MPa.Finally,the pre-separation-extraction-decantation process separates the mixture of dimethyl carbonate and methanol generated in the synthesis stage with 99.11%purity of dimethyl carbonate.Above results verify the feasibility of producing dimethyl carbonate from the perspective of multi-scale simulation and realize the multi-level utilization of biomass resources.
