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分子动力学模拟水分对小分子糖玻璃态转变温度及扩散性质的影响周国辉，刘成梅，万婕，艾亦旻，王玲华，罗达文（南昌大学食品科学与技术国家重点实验室，江西南昌 330047）摘要：为了预测水分对蔗糖、海藻糖等小分子糖玻璃态温度和扩散系数的影响，在恒温恒压（NPT）系综和COMPASS力场条件下，利用分子动力学模拟方法，通过模拟小分子糖体系在180~460 K温度范围内的比体积，与对应的温度作图，获得不同水分含量下小分子糖的玻璃态转变温度；在298 K下，模拟得到在不同水分含量下糖体系中水分子的均方位移（MSD），分析了水分对小分子糖扩散性质的影响；同时研究了温度为298 K，水分含量为5.0%时，小分子糖体系中氧原子与水中氧原子之间的径向分布函数。
研究结果表明：在相同水分含量下，海藻糖的玻璃态转变温度大于蔗糖，海藻糖与水分子形成氢键的能力要大于蔗糖；随着水分含量的增加，两种糖模型的T g都呈现显著下降趋势，水分子更容易在糖模型中扩散，与糖分子发生相互作用的概率增大。
关键词：分子动力学；玻璃态转变温度；蔗糖；海藻糖；扩散系数；径向分布函数文章篇号：1673-9078(2014)9-154-160 DOI: 10.13982/j.mfst.1673-9078.2014.09.026 Effect of Moisture Content on Glass Transition Temperature andDiffusion Properties of Low-molecular-weight Sugars by MolecularDynamics SimulationZHOU Guo-hui, LIU Cheng-mei, WAN Jie, AI Yi-min, WANG Ling-hua, LUO Da-wen (State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China) Abstract: In this study, the effect of different moisture contents on glass transition temperature (T g) and diffusion properties of low-molecular-weight sugars (such as sucrose and trehalose) were evaluated, using the COMPASS force field and isothermal-isobaric (NPT) ensemble. Molecular dynamics simulation was used to obtain the glass transition temperatures of sugars by simulating a plot of the specific volume of low-molecular-weight sugar in a temperature range of 180 K to 460 K versus the corresponding temperature. At 298 K, the mean square displacement (MSD) of water molecules in the sugar systems with varying moisture content was simulated, and the effect of moisture content on the diffusion properties was analyzed. In addition, when the temperature was 298K and the moisture content was 5%, the radial distribution function (RDF) of ox ygen atoms in water and in the low-molecular-weight sugar system was studied. The results indicated that the value of T g and the ability to form hydrogen bonds with water molecules were higher for trehalose than for sucrose at the same moisture content. With increasing moisture content, the value of T g in the two sugar models showed a significant downward trend, water molecules more easily diffused into the sugar systems, and the chance to interact with sugar molecules increased.Key words: molecular dynamics; glass transition temperature; sucrose; trehalose; diffusion coefficient; radial distribution function玻璃化转变是指非晶态物质从玻璃态到橡胶态或橡胶态到玻璃态的转变，其转变温度称之为玻璃化转变温度(T g)，其与物质储藏稳定性有着重要的联系[1]。
氮化硅表面DLC膜压痕过程的分子动力学模拟李军;古乐;郑德志【摘要】10.3969/j.issn.0254-0150.2012.09.003% 对β-Si 3 N4基体表面DLC薄膜压痕过程进行分子动力学模拟。
压入过程模拟采用刚性球形压头与Tersoff势函数，考虑薄膜密度、膜厚、压入深度和基体属性对压痕过程的影响。
模拟结果显示：薄膜抗压变形能力随着薄膜密度增加而变强，随着薄膜厚度增加而变弱；随压入深度增加，接触区内原子平均势能增加并转化为动能，导致温度升高，DLC膜中sp3键比例和配位数为5原子数增加，薄膜硬度增加。
β-Si 3 N4基体属性对薄膜压痕特性产生影响，高硬度基体表面D L C膜的抗压变形能力更强，但随薄膜厚度增加其影响逐渐减弱。
【期刊名称】《润滑与密封》【年(卷),期】2012(000)009【总页数】6页(P10-14,27)【关键词】类金刚石碳膜;氮化硅;纳米压痕;分子动力学模拟【作者】李军;古乐;郑德志【作者单位】哈尔滨工业大学机电工程学院黑龙江哈尔滨150001;哈尔滨工业大学机电工程学院黑龙江哈尔滨150001;哈尔滨工业大学机电工程学院黑龙江哈尔滨150001【正文语种】中文【中图分类】TH117微纳米尺度的DLC膜广泛应用于磁光存储介质、光学窗口、轴承、生物医学和微电机装置中［1］。
薄膜在纳米尺度往往表现出与宏观尺度不同的力学性能，仅从连续介质的角度进行研究已经难以深入地了解纳米尺度薄膜的力学性能，必须从纳米尺度或原子水平上对其进行研究。
纳米压痕是一种广泛使用的材料性能测试方法。
在压痕试验中，压入深度一般在纳米尺度范围，压痕分析和建模时假设工件厚度为无限。
然而对于本身已经是纳米尺度薄膜，其尺寸效应和基体对薄膜机械性能的影响已经不可忽略。
分子动力学(Molecular Dynamics，MD)模拟是一种有效地研究材料性能的方法，广泛应用于化学、材料科学。
Nair等［2］应用分子动力学模拟不同厚度的纳米尺度Ni薄膜压痕的压痕过程，揭示了位错形成的条件;Fang等［3］通过分子动力学模拟金表面自组装膜的压痕过程，分析了压入深度、温度、自组装膜层数、压头形状等对压痕过程的影响机制;Cheong等［4］应用分子动力学模拟了Si基底上覆盖DLC膜的纳米压痕过程，发现纳米压痕过程与微米尺度的压痕过程的机制有很大的不同，膜厚影响膜和基体的塑性变形的机制。
分子动力学模拟英语Molecular dynamics simulations are an incredible tool that allows us to peek into the microscopic world. It'slike having a virtual microscope that can show us how molecules move and interact in real time.The beauty of molecular dynamics simulations is that they're not just theoretical. They use complex algorithms and powerful computers to model the behavior of molecules in a system, whether it's a protein in a cell or a gas in a container.One of the coolest things about these simulations is that they can help us understand processes that aredifficult to observe directly. For example, we can use them to study how drugs interact with their targets, which can aid in drug design.And it's not just scientists who find molecular dynamics simulations fascinating. Engineers use them tounderstand material properties and how materials behave under extreme conditions. Even biologists can benefit from them by studying biological processes at the molecular level.The accuracy of these simulations depends a lot on the force fields and algorithms used. But with the advances in computing power and simulation techniques, we're getting closer and closer to accurately predicting the behavior of complex systems.So in a nutshell, molecular dynamics simulations are a powerful way to understand the world at the molecular level. They're like a window into the microscopic realm, helpingus uncover secrets that were once hidden from view.。
分子动力学模拟小分子自组装英文回答：Molecular dynamics (MD) simulations are a powerful tool for studying the self-assembly of small molecules. MD simulations can provide detailed information about the structure, dynamics, and thermodynamics of self-assembled systems. This information can be used to understand the mechanisms of self-assembly and to design new self-assembled materials.MD simulations of small molecule self-assemblytypically involve the following steps:1. Create a molecular model: The first step is to create a molecular model of the small molecule. This model can be created using a variety of software programs.2. Prepare the simulation system: The next step is to prepare the simulation system. This involves specifying thesimulation box size, the number of molecules in the system, and the simulation conditions (e.g., temperature, pressure).3. Run the simulation: Once the simulation system is prepared, the MD simulation can be run. The simulation will typically run for several nanoseconds or microseconds.4. Analyze the simulation results: The final step is to analyze the simulation results. This involves extracting information about the structure, dynamics, and thermodynamics of the self-assembled system.MD simulations have been used to study a wide varietyof small molecule self-assembled systems. These systems include micelles, vesicles, liquid crystals, and gels. MD simulations have provided valuable insights into the mechanisms of self-assembly and the properties of self-assembled materials.中文回答：分子动力学(MD)模拟是小分子自组装研究的有力工具。
分子动力学模拟流程Molecular dynamics simulation is a powerful tool in the field of computational chemistry and physics. It allows researchers to study the movement of atoms and molecules over time, providing valuable insights into the behavior of materials at the molecular level. By simulating the interactions between particles based on classical mechanics, scientists can explore various physical and chemical processes in great detail.分子动力学模拟是计算化学和物理领域中一种强大的工具。
它允许研究人员随着时间的推移研究原子和分子的运动，为在分子水平上材料的行为提供有价值的见解。
通过基于经典力学对粒子之间的相互作用进行模拟，科学家可以详细地探索各种物理和化学过程。
One of the key advantages of molecular dynamics simulation is its ability to capture the dynamics of complex systems that are difficult to study experimentally. By monitoring the trajectories of individual particles in a simulated environment, researchers can observe how macroscopic properties emerge from the interactions of atoms and molecules. This information is crucial for understanding the behaviorof materials under different conditions and for designing new materials with desired properties.分子动力学模拟的一个关键优势是它能够捕获实验难以研究的复杂系统的动态。
mof膜构效关系分子动力学模型Molecular dynamics (MD) simulation is a computational modeling technique used to study the behavior and properties of molecules at the atomic level. It can provide insights into the structure, dynamics, and thermodynamics of molecular systems, including the interaction between molecules and their surrounding environment.在研究薄膜构效关系方面，分子动力学模型在提供精细的原子层面的信息方面非常有用。
通过模拟材料中的原子和分子之间的相互作用以及它们与表面之间的交换，可以理解薄膜材料的物理和化学性质。
To investigate the mof膜构效关系 using MD simulations, one needs to start by constructing an appropriate model of the MOF membrane system. This involves representing the MOF structure as a collection of atoms and assigning appropriate force field parameters that describe the interatomic interactions. The force field parameters determine how atoms interact with each other within the system and with any surrounding molecules or surfaces.要通过分子动力学模拟研究MOF膜构效关系，首先需要建立合适的MOF膜体系模型。
第５０卷第２期２０２１年２月人 工 晶 体 学 报ＪＯＵＲＮＡＬＯＦＳＹＮＴＨＥＴＩＣＣＲＹＳＴＡＬＳＶｏｌ．５０ Ｎｏ．２Ｆｅｂｒｕａｒｙ，２０２１ＳｉＯ２气凝胶分子动力学模拟研究进展杨 云，史新月，吴红亚，秦胜建，张光磊（石家庄铁道大学材料科学与工程学院，石家庄 ０５００４３）摘要：二氧化硅（ＳｉＯ２）气凝胶是一种拥有三维骨架网络结构的纳米多孔材料，具有高孔隙率、低密度和低热导率等许多独特的性能。
但是由于二氧化硅气凝胶本身的脆性及高温稳定性差等原因，限制了其大规模应用。
二氧化硅气凝胶的热力学性能与其内部的三维骨架和孔结构紧密相关，掌握二氧化硅气凝胶内部微结构演化规律与宏观性能的关联，是改善其热力学性能的前提。
分子动力学模拟可以从原子层面分析和探索气凝胶的结构并预测其热力学性能。
本文对分子动力学模拟下二氧化硅气凝胶势函数、多孔结构建模、结构表征、力学性能和热性能方面进行了详细总结，有助于从原子层面解释二氧化硅气凝胶结构与性能之间的关系，为从成分和结构方面设计气凝胶提供一种理论指导方法。
关键词：ＳｉＯ２气凝胶；分子动力学；微结构；力学性能；热性能中图分类号：ＴＱ４２７文献标志码：Ａ文章编号：１０００ ９８５Ｘ（２０２１）０２ ０３９７ １０ＲｅｓｅａｒｃｈＰｒｏｇｒｅｓｓｉｎＭｏｌｅｃｕｌａｒＤｙｎａｍｉｃｓＳｉｍｕｌａｔｉｏｎｏｆＳｉＯ２ＡｅｒｏｇｅｌｓＹＡＮＧＹｕｎ，ＳＨＩＸｉｎｙｕｅ，ＷＵＨｏｎｇｙａ，ＱＩＮＳｈｅｎｇｊｉａｎ，ＺＨＡＮＧＧｕａｎｇｌｅｉ（ＳｃｈｏｏｌｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅｒｉｎｇ，ＳｈｉｊｉａｚｈｕａｎｇＴｉｅｄａｏＵｎｉｖｅｒｓｉｔｙ，Ｓｈｉｊｉａｚｈｕａｎｇ０５００４３，Ｃｈｉｎａ）Ａｂｓｔｒａｃｔ：Ｓｉｌｉｃａａｅｒｏｇｅｌｓａｒｅｎａｎｏｐｏｒｏｕｓｍａｔｅｒｉａｌｓｗｉｔｈｔｈｒｅｅ ｄｉｍｅｎｓｉｏｎａｌｆｒａｍｅｗｏｒｋｎｅｔｗｏｒｋｓｔｒｕｃｔｕｒｅ．Ｓｉｌｉｃａａｅｒｏｇｅｌｓｈａｖｅｍａｎｙｕｎｉｑｕｅｐｒｏｐｅｒｔｉｅｓｓｕｃｈａｓｈｉｇｈｐｏｒｏｓｉｔｙ，ｌｏｗｄｅｎｓｉｔｙ，ｌｏｗｔｈｅｒｍａｌｃｏｎｄｕｃｔｉｖｉｔｙａｎｄａｃｏｕｓｔｉｃａｌｉｎｓｕｌａｔｉｏｎｐｒｏｐｅｒｔｉｅｓ．Ｈｏｗｅｖｅｒ，ｄｕｅｔｏｔｈｅｐｏｏｒｍｅｃｈａｎｉｃａｌｐｅｒｆｏｒｍａｎｃｅｏｆｓｉｌｉｃａａｅｒｏｇｅｌｓｓｕｃｈａｓｂｒｉｔｔｌｅｎｅｓｓａｎｄｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｉｎｓｔａｂｉｌｉｔｙ，ｔｈｅｌａｒｇｅ ｓｃａｌｅｃｏｍｍｅｒｃｉａｌａｐｐｌｉｃａｔｉｏｎｏｆｓｉｌｉｃａａｅｒｏｇｅｌｓｉｓｌｉｍｉｔｅｄ．Ｔｈｅｔｈｅｒｍｏｄｙｎａｍｉｃｐｒｏｐｅｒｔｉｅｓｏｆｓｉｌｉｃａａｅｒｏｇｅｌｓａｒｅｒｅｌａｔｅｄｔｏｔｈｅｉｒｔｈｒｅｅ ｄｉｍｅｎｓｉｏｎａｌｌｉｇａｍｅｎｔｎｅｔｗｏｒｋａｎｄｐｏｒｅｓｔｒｕｃｔｕｒｅ．Ｅｘｐｌｏｒｉｎｇｔｈｅｒｅｌａｔｉｏｎｓｈｉｐｂｅｔｗｅｅｎｍｉｃｒｏｓｔｒｕｃｔｕｒｅｅｖｏｌｕｔｉｏｎａｎｄｍａｃｒｏｓｃｏｐｉｃｐｒｏｐｅｒｔｉｅｓｏｆｓｉｌｉｃａａｅｒｏｇｅｌｓｉｓｅｓｓｅｎｔｉａｌｆｏｒｉｍｐｒｏｖｉｎｇｔｈｅｉｒｔｈｅｒｍｏｄｙｎａｍｉｃｐｒｏｐｅｒｔｉｅｓ．Ｍｏｌｅｃｕｌａｒｄｙｎａｍｉｃｓ（ＭＤ）ｓｉｍｕｌａｔｉｏｎｓａｒｅａｎａｐｐｒｏｐｒｉａｔｅｔｏｏｌｆｏｒｔｈｅｓｔｕｄｙｏｆｍｅｃｈａｎｉｃａｌｐｒｏｐｅｒｔｉｅｓｆｒｏｍｔｈｅａｔｏｍｉｓｔｉｃｌｅｖｅｌ．Ｂａｓｅｄｏｎｔｈｅａｃｃｕｒａｔｅｐｏｔｅｎｔｉａｌ，ＭＤｓｉｍｕｌａｔｉｏｎｓｈａｖｅｃｏｒｒｅｃｔｌｙｐｒｅｄｉｃｔｅｄｔｈｅｐｏｗｅｒｌａｗｔｈａｔｒｅｌａｔｅｓｔｈｅｒｍａｌｃｏｎｄｕｃｔｉｖｉｔｙａｎｄｄｅｎｓｉｔｙ．ＭＤｓｉｍｕｌａｔｉｏｎｓａｌｓｏａｎａｌｙｚｅａｅｒｏｇｅｌｓｔｒｕｃｔｕｒｅｆｒｏｍｔｈｅａｔｏｍｉｓｔｉｃｌｅｖｅｌａｎｄｐｒｅｄｉｃｔｔｈｅｉｒｔｈｅｒｍｏｄｙｎａｍｉｃｐｅｒｆｏｒｍａｎｃｅ．Ｔｈｅｉｎｔｅｒａｔｏｍｉｃｐｏｔｅｎｔｉａｌ，ｐｏｒｅｓｔｒｕｃｔｕｒｅｇｅｎｅｒａｔｉｏｎ，ｓｔｒｕｃｔｕｒａｌｃｈａｒａｃｔｅｒｉｚａｔｉｏｎ，ｍｅｃｈａｎｉｃａｌｐｒｏｐｅｒｔｉｅｓａｎｄｔｈｅｒｍａｌｃｏｎｄｕｃｔｉｖｉｔｙｏｆｔｈｅｓｉｌｉｃａａｅｒｏｇｅｌｓｆｒｏｍｔｈｅａｓｐｅｃｔｏｆＭＤｓｉｍｕｌａｔｉｏｎｓａｒｅｓｕｍｍａｒｉｚｅｄ．Ｔｈｉｓｗｏｒｋｃｏｎｔｒｉｂｕｔｅｓｔｏｅｘｐｌａｉｎｉｎｇｔｈｅｒｅｌａｔｉｏｎｓｈｉｐｂｅｔｗｅｅｎｔｈｅｓｔｒｕｃｔｕｒｅａｎｄｐｒｏｐｅｒｔｉｅｓｏｆｓｉｌｉｃａａｅｒｏｇｅｌｓｆｒｏｍｔｈｅａｔｏｍｉｓｔｉｃｌｅｖｅｌ，ｗｈｉｃｈｃａｎｐｒｏｖｉｄｅａｔｈｅｏｒｅｔｉｃａｌｇｕｉｄａｎｃｅｆｏｒｄｅｓｉｇｎｉｎｇｓｉｌｉｃａａｅｒｏｇｅｌｓｉｎｔｅｒｍｓｏｆｃｏｍｐｏｓｉｔｉｏｎａｎｄｓｔｒｕｃｔｕｒｅ．Ｋｅｙｗｏｒｄｓ：ＳｉＯ２ａｅｒｏｇｅｌ；ｍｏｌｅｃｕｌａｒｄｙｎａｍｉｃ；ｍｉｃｒｏｓｔｒｕｃｔｕｒｅ；ｍｅｃｈａｎｉｃａｌｐｒｏｐｅｒｔｙ；ｔｈｅｒｍａｌｐｒｏｐｅｒｔｙ 收稿日期：２０２０ １０ ２１ 基金项目：国家自然科学基金（５１５０２１７９）；河北省自然科学基金（Ｅ２０２０２１００７６） 作者简介：杨 云（１９９２—），女，河北省人，硕士研究生。
分子动力学模拟计算氢键作用英文回答：Molecular dynamics simulation is a powerful tool for studying the behavior of molecules and their interactions. When it comes to studying hydrogen bonding, molecular dynamics simulations can provide valuable insights into the dynamics and stability of these interactions.In a molecular dynamics simulation, the behavior of molecules is modeled over time based on the laws of physics. This allows us to observe how hydrogen bonds form, break, and fluctuate between different molecules. By analyzing the trajectories of the molecules, we can gain a better understanding of the strength and dynamics of hydrogen bonding.One common approach to studying hydrogen bonding in molecular dynamics simulations is to use force fields that explicitly account for the electrostatic and van der Waalsinteractions involved in hydrogen bonding. These force fields allow us to calculate the energy associated with hydrogen bonding and track its changes over the course of the simulation.Furthermore, by analyzing the radial distribution functions of hydrogen bonds, we can determine the average distance and coordination number of hydrogen bonds in the system. This provides valuable information about the structure and dynamics of hydrogen bonding networks.In addition to studying the behavior of hydrogen bonds in bulk systems, molecular dynamics simulations can also be used to investigate the role of hydrogen bonding inspecific chemical reactions or biological processes. For example, simulations can help elucidate the impact of hydrogen bonding on the stability of protein structures or the mechanism of enzymatic reactions.Overall, molecular dynamics simulations offer a powerful means of investigating the behavior of hydrogen bonds at the molecular level, providing valuable insightsthat can complement experimental studies.中文回答：分子动力学模拟是研究分子及其相互作用行为的强大工具。
分子动力学amber英语Molecular Dynamics Simulations: A Primer.Molecular dynamics (MD) simulations are a powerful tool for studying the behavior of molecules and materials at the atomic level. MD simulations use classical mechanics to calculate the positions and velocities of individual atoms and molecules over time, allowing researchers to observe how these systems evolve and interact.How MD Simulations Work.MD simulations begin with the creation of a molecular model, which is a representation of the system being studied. The model includes the positions and velocities of all the atoms in the system, as well as the forces that act between them. The forces are calculated using a force field, which is a mathematical model that describes the potential energy of the system as a function of the atomic positions and velocities.Once the molecular model has been created, the MD simulation is run by integrating the equations of motionfor the atoms over time. This integration is typically performed using a numerical method, such as the Verlet algorithm. The integration step size is typically on the order of femtoseconds (10^-15 seconds), which is small enough to accurately capture the motions of the atoms.As the MD simulation progresses, the positions and velocities of the atoms are updated at each time step. This allows researchers to track the evolution of the system over time and observe how the atoms interact with each other.Applications of MD Simulations.MD simulations have a wide range of applications in chemistry, biology, and materials science. Some of the most common applications include:Protein folding: MD simulations can be used to studythe folding pathways of proteins, which is important for understanding how proteins function.Drug design: MD simulations can be used to predict how drugs will bind to proteins, which can help in the development of new drugs.Materials science: MD simulations can be used to study the properties of materials, such as their strength, toughness, and thermal conductivity.Chemical reactions: MD simulations can be used to study chemical reactions, such as the formation and breaking of bonds.Limitations of MD Simulations.MD simulations are a powerful tool, but they also have some limitations. One limitation is that MD simulations are computationally expensive. This is because the integration of the equations of motion for the atoms over time requires a significant amount of computing power. As a result, MDsimulations are often limited to relatively small systems and short time scales.Another limitation of MD simulations is that they are based on classical mechanics. This means that MD simulations do not take into account quantum effects, which can be important for some systems.Future of MD Simulations.MD simulations are a rapidly growing field, and there are a number of new developments that are making MD simulations more powerful and accessible. One of the most important developments is the use of graphics processing units (GPUs) to accelerate MD simulations. GPUs are specialized processors that are designed for performing large numbers of calculations in parallel, which makes them ideal for MD simulations.The use of GPUs has made it possible to perform MD simulations on much larger systems and for longer time scales than was previously possible. This has opened up newpossibilities for studying complex biological systems and materials.Another important development in MD simulations is the development of new force fields. Force fields are the mathematical models that describe the potential energy of the system as a function of the atomic positions and velocities. The accuracy of MD simulations depends on the accuracy of the force field.New force fields are being developed that are more accurate and that can be used to study a wider range of systems. This is making MD simulations an even more powerful tool for studying the behavior of molecules and materials at the atomic level.。
水银的蒸发实验报告引言蒸发是一种物质由液态转化为气态的过程。
在自然界中，许多物质都可以发生蒸发现象，其中水银是一种常见且重要的金属元素。
本实验旨在研究水银的蒸发速度与温度之间的关系，以增进对水银蒸发规律的了解。
实验目的1. 研究水银的蒸发速度与温度之间的关系；2. 分析温度对水银蒸发速度的影响。
实验步骤1. 准备实验器材：水银、烧杯、温度计、实验平台等；2. 将烧杯中加入适量的水银，并记下初始体积；3. 将烧杯放置于实验平台上，使用温度计测量室温，记录下初始温度；4. 将实验平台的温度逐渐升高，每升高5记录一次水银的体积和温度；5. 直到水银完全蒸发为止，停止温度的升高。
实验结果以下表格列出了实验过程中不同温度下水银体积的变化：温度（）水银体积（ml）20 10.025 9.830 9.635 9.340 9.045 8.850 8.555 8.260 7.965 7.670 7.375 7.080 6.785 6.390 6.095 5.6100 5.2数据分析与讨论根据实验数据，我们可以绘制出温度与水银体积的关系图。
从图中可以看出，在温度逐渐升高的过程中，水银的体积呈逐渐减少的趋势。
随着温度的升高，水银蒸发速度增加，导致体积缩小。
蒸发速率与温度呈正相关关系，随着温度的提高，水银分子的热运动加剧，有更大的机会从液态转化为气态。
通过实验数据的分析，我们可以得出结论：水银的蒸发速率与温度呈正相关关系。
随着温度的升高，水银的蒸发速率增加。
这一结论与蒸发过程的热力学性质相符合。
然而，需要注意的是，水银是一种有毒物质，应该避免直接接触和吸入。
在进行水银蒸发实验时，应采取必要的安全措施，如佩戴防护手套和口罩等。
结论本实验通过研究水银的蒸发速度与温度之间的关系，得出了以下结论：1. 水银的蒸发速率与温度呈正相关关系，即随着温度的升高，水银的蒸发速率增加；2. 实验结果与蒸发过程的热力学性质相符合。
A molecular dynamics study about graphite and boron coated graphite at reactortemperaturesTurgay Korkut ⇑Faculty of Science and Art,Department of Physics,Ibrahim Cecen University,04100Ag˘rı,Turkey a r t i c l e i n f o Article history:Received 7March 2013Received in revised form 21July 2013Accepted 25July 2013Keywords:GraphiteBoron coating Nuclear reactor Moderator ReflectorMolecular dynamicsa b s t r a c tNuclear graphite is exclusively produced as a moderator and reflector material in nuclear industry.It haslow density,high strength,low thermal expansion,high thermal conductivity,high hardness and good thermal resistance.We simulated graphite structure in a box using LAMMPS (Large-scale Atomic/Molec-ular Massively Parallel Simulator)to obtain heat flux,atomic displacements,pressures and total energy values for 300K (room temperature),1273K (gas-cooled reactor operating temperature)and graphite temperatures in the reactor (from 573K to 1123K).Also boron coated graphite (BCG)was investigated by the same method and to estimate the same parameters.Ó2013Elsevier Ltd.All rights reserved.1.IntroductionNuclear graphite has several special features such as low neutron absorption rate,high thermal conductivity and high-tem-perature strength and stability.It is high purity synthetic graphite.Also the density of nuclear graphite (1.74–1.85)is lower than graphite (2.09–2.23).It slows down neutrons which are produced during the fission process.It is generally used in nuclear reactors as moderator,reflector and structural material.Its thermal proper-ties are an important issue for the nuclear reactor designer.Recently in literature there are many studies about nuclear graphite material.Some of these studies,thermal parameters of nuclear graphite and properties of nuclear graphite under different irradiation conditions in the foreground.Contescu et al.investi-gated relationship between nuclear graphite microstructure and its oxidation resistance.In this study,it was reported that nuclear graphite may be a candidate for use in the very high temperature gas-cooled reactors (Contescu et al.,2012).Zhmurikov et al.studied the thermophysical properties of three different graphite compos-ites from 300K to 1675K.Heat capacities and thermal conductiv-ity values of samples were given (Zhmurikov et al.,2012).Yang et al.implemented H +ion irradiation on nuclear graphite samples.They determined surface deformations and reported XRD and Ra-man spectroscopic results about their experiments (Yang et al.,2012a,b ).In terms of next generation nuclear reactor plans micro-structural properties of nuclear graphite was evaluated (Karthik et al.,2012).In another paper,interactions between nuclear graphite and molten fluoride salts at 773K were investigated by synchrotron X-ray diffraction and carbon K-edge X-ray absorption near-edge structure (Yang et al.,2012a,b ).To determine stress analysis and lifetime prediction of nuclear graphite,several creep models for irradiation responses to it were investigated.As a result of this study,the Kennedy model considered compared to other models for the HTR process (Fang et al.,2012).Statistical analysis via three distributions of experimental results about nuclear graphite strength tests were made by researchers (Hindley et al.,2012).A study was performed about the successful recycle of irradiated graphite to fabricate new nuclear graphite (Burchell and Pappano,2012).Molecular dynamics simulations at high temperatures (up to 1800K)was made and this paper focused on especially threshold displacement energy of graphite by MSD (mean square displacements)calculations (Hehr et al.,2007).In the reactor applications coating of materials with boron and boron compounds such as B 4C is widespread.Boron coated graphite for fusion reactor applications was produced.In this study,boron coating was suggested a suitable candidate for the first wall and limiter coatings in toroidal magnetically confined fusion reactors (Pierson and Mullendore,1979).B 4C coating has been suggested fusion devices of next generation ITER and DEMO (Buzhinskij and Semenets,1999;Buzhinskij and Otroshchenko,2011).For the first wall of W7-X thick B 4C coating was developed (Kötterl et al.,2001).Four types of B 4C/Mo based composite coating for fusion applications was performed (Lin et al.,2013).0306-4549/$-see front matter Ó2013Elsevier Ltd.All rights reserved./10.1016/j.anucene.2013.07.036Tel.:+905058746273.E-mail address:turgaykorkut@temperature,gas-cooled reactor operating temperature(1273K)(Samolyuk et al.,2011)and nuclear graphite temperatures in the reactor.In these temperatures atomic arrangements,energy val-ues,heatfluxes,pressures and atomic displacements were given.2.Molecular dynamics simulationsMolecular dynamics is a method for computer simulation of complex systems including atoms,bonds,angles,dihedrals,etc., modeled at the atomic level.Numeric solutions by MD are based on the Newton’s equations of motion mentioned below as Eqs.(1)and(2).F i¼m iÁa i¼m iÁdV i=dt¼md2r i=dt2ð1ÞF i¼ÀGRAD i Eð2ÞGenerally molecular dynamics simulations consist of four steps as(1)system setup,(2)equilibration,(3)simulation run and(4) output and data analysis.In the1990s,a large-scale parallel classical MD code LAMMPS started to develop by Sandia National Laboratory(Plimpton, 1995).It is an open source code and it is updated regularly.It can run on a single processor or as parallel.An input script should be written by the user to run LAMMPS.In the input script there are molecular properties such as lattice parameters and atomic masses of desired material.Also selecting potentials to be used is a very important issue in LAMMPS.To define atomic coordinates for each atom type,several commands can be used or a datafile can be written.The MD simulations were performed in LAMMPS using a time step of0.005fs.We wrote an input script including graphitestructure with hexagonal2.462Ålattice constant.For the boron coating hexagonal form of boron atoms with4.908Ålattice con-stant are modeled.We used tersoff potential including potential parameters of B–B,B–C and C–C interactions(Tersoff,1994). 19,152Carbon atoms and1232boron atoms are created in an orthogonal simulation box(0,À85.0091,À4.908)to(274.848, 85.0091,4.908)using by a datafile via VMD visualization tool (Humphrey et al.,1996).In simulations LAMMPS metal units are used(Angstrom,gram,picoseconds).Periodic boundary conditions carried out along the x,y,z directions.The microcanonical ensem-ble(NVE)withfix temp/rescale command was used as thermostat. Several output parameters such as heatflux,total energy,pres-sures and atomic displacements are written in the input script.Fi-nally,molecular dynamics is run for10,000numbers of time steps.Fig.3.Atomic displacements for graphite(a)300K,(b)1273K,and(c)573–11233.Results and discussionTo get information about the responses of nuclear graphite against reactor temperatures and thermal effects of boron coating on the graphite structure we wrote a LAMMPS inputfile.We wanted several output parameters as a function of the number of time steps such as total energy distribution,heatfluxes,pressures and atomic displacements.Also arrangements of carbon and boron atoms in bare and BCG are modeled using VMD tool.Fig.1a–c shows the status of carbon atoms in the bare graphite structure after300K,1273K and heating from573K to1123K exposure respectively.As similar to Figs.1and2a–c shows theFig.6.Total energy curves for BCG(a)300K,(b)1273K,(c)573–1123K.arrangements of boron and carbon atoms in the BCG structure.As can be seen these atomic arrangements,it can be said that the atomic structure of graphite was not affected from these tempera-tures.For B coating graphite,there is a slight deformation in the boron–graphite interface at all of the used temperatures.There is no separation or break completely.LAMMPS can estimate the current displacement of each atom in the structure from its original coordinates including all effects due to atoms passing.Figs.3a–c and4a–c show atomic displacement values for graphite and BCG,respectively at three different temper-ature conditions.For300K maximum displacement values were obtained as0.027for graphite and0.0067for BCG structure.AsFig.7.Pressures for graphite(a)300K,(b)1273K,and(c)573–1123K.shown,the atomic displacement value is a result of boron coating could be called four times reduced.For1273K temperature,dis-placement values approximately same for graphite and BCG struc-tures.After heating process displacement value of graphite is lesser than BCG.Total energy plots of three graphite and BCG systems(300K, 1273K,573–1123K)as a function of the number of time steps are shown in Figs.5a–c and6a–c.For room temperature,peaks of total energy values are approximately16,000and1500electron volts for graphite and BCG structures.Boron coating has been re-duced total energy at this temperature.As similar this state,the to-tal energy of graphite system is higher than BCG at other two temperature conditions.This result is important in terms of energy efficiency of BCG system.Pressure values can be seen in Figs.7a–c and8a–c for graphite and BCG respectively for three different temperature values. Graphite has higher pressure values than BCG system at three tem-perature conditions.Heatflux(J)is the rate of heat-energy transfer through a given surface.Finally heatflux curves are given in Figs.9a–c and10a–c. At room temperature,graphite has very low negative heatflux.For BCG system J isfluctuating betweenÀ0.1and0.2eV/p s A2values. For two systems J is stable around zero with very smallfluctuations at1273K.But there is a sudden decrease for BCG around1000time steps.At heating state from573K to1123K,J is approximately sta-ble around zero withfluctuations caused by the temperature dif-ference.It can be said that from MD results,the boron coating process did not affect heatflow.4.ConclusionsGraphite is a material including carbon atoms widely used in many different areas.Graphite is generally used in nuclear reactors (especially gas-cooled reactors)as a reflector,neutron moderator and structural material.In this paper responses of graphite against reactor temperatures are evaluated.Several parameters such as displacements,heatfluxes,pressures,total energies are presented by LAMMPS molecular dynamic simulations.As a result,stability of graphite against reactor operating temperature is reported.Also to see the effects of boron coating on graphite structure, boron coated graphite system(BCG)was simulated in the same molecular dynamics conditions at three different temperatures. 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