Simulation of phase transition process using lattice Boltzmann method

A new lattice Boltzmann model based on SC model, is proposed to describe the liquid-vapor phase transitions. The new model is validated through the simulation of the one-component phase transition process. Compared with the simulation results of van der Waals gas and the Maxwell equal-area construction, the results of the new model have a better agreement with the analytical solutions than those of SC and Zhang models. Since the obtained temperature range and the maximum density ratio in this model are expanded, and the magnitude of maximum spurious current is only between those of SC and Zhang models, it is believed that this new model has better stability than SC and Zhang models. Consequently, the application scope of this new model is expanded compared with the existing phase transition models. According to the principle of the corresponding states in engineering thermodynamics, the simulations of ammonia and water phase transition process were implemented using this new model with different equations of state. Compared with the experimental data of ammonia and water, the results show that the Peng-Robinson is the best equation of state to describe the phase transition process of ammonia and water. Especially, the simulation results of ammonia with Peng-Robinson equation of state have an excellent agreement with its experimental data. Therefore these simulation results have a significant influence on the real engineering applications.     

气体沿任意过程的热力学性质

 导出气体沿任意过程的热容、膨胀系数、压强系数和压缩系数等重要热力学参量的普遍表达式,并以范德瓦尔斯方程和一个推广的RK方程为例,讨论实际气体沿一些具体过程的热力学性质.所得的结果不仅可推出文献中已有的一些重要内容,而且还可导出一些有意义的新结论.     

燃料电池电动汽车氢消耗量的计算

针对“清能3号”燃料电池电动汽车在一次国际性比赛上所给出的燃料经济性指标结果,比较了用van derW aa ls方程和氢气压缩系数计算氢气质量的两种方法。通过计算得出了合理的燃料经济性指标,指出赛会组织者应用van derW aa ls方程计算燃料经济性指标有误,同时建议使用压缩系数法。给出了由气体压强p、体积V和温度T计算气体质量m的解析解,列出了在压强、体积采用不同单位时,对应的普适气体常数R和改正项a、b的数值,为求解van derW aa ls方程提供了方便。     

CO2气体等焓膨胀的焦耳-汤姆逊效应

运用van der Waals状态方程讨论焦汤系数和转换温度,通过对CO2实际气体等焓膨胀的焦汤系数及转换温度与van der Waals理论值比较发现,CO2实际气体的焦汤系和转换温度与理论值偏差不大,基本能反映实际气体的焦耳-汤姆逊的各种基本关系,可应用于一般热力学的定性分析。     

Coupling mechanism of multi-force interactions in the myosin molecular motor

The dynamics of the myosin molecular motor as it binds to actin filaments during muscle contraction are still not clearly understood. In this paper, we focus on the coupling mechanism of multi-force interactions in the myosin molecule during its interaction with actin. These forces include the electrostatic force, the van der Waals force and the Casimir force in molecular dynamic simulations of the molecules in solvent with thermal fluctuations. Based on the Hamaker approach, van der Waals and Casimir potentials and forces are calculated between myosin and actin. We have developed a Monte Carlo method to simulate the dynamic activity of the molecular motor. We have shown that because of the retardation effect, the van der Waals force falls into the Casimir force when the distance between the surfaces is larger than 3 nm. When the distance is smaller than 3 nm, the electrostatic force and the van der Waals force increase until the myosin becomes attached to the actin. Over the distances studied in the present work, the electrostatic force dominates the attractive interactions. Our calculations are in good agreement with recently reported experimental results.     

氯化氢与乙烯加成反应中化学键动态转变的图像

利用从头算方法研究了氯化氢(HCl)与乙烯(CH2CH2, C2H4)的加成反应。依据分子形貌(MF)理论,计算得到了分子中一个电子所受到的作用势(PAEM)及Dpb,研究了该反应过程中化学键的形成、断裂及范德华相互作用。在分子中紧邻的两原子之间,如果两原子间的Dpb值比体系的电离能大,表明两者之间主要是成键相互作用,反之是范德华相互作用。研究表明,MF理论能够很好地描述分子间的这种范德华作用,并能够特征化化学键的形成或断裂,进而为分子间的化学键形成或断裂提供新的转变图像。     

含环己酮二元体系过量体积的实测和过量体积与过量焓的关联方程

用经过改进的连续稀释法测定了尚未见报道的六个含环己酮二元体系在293.15K(及298.15K的过量体积,经与已知标准物系数据的比较,验证了实验方法的可靠性。所得实验数据用关联方程式进行拟合,得出了各体系的拟合参数值。以范德华方程为基础,推导了过量体积与过量焓的关联方程。根据这一方程,分析了压力和过量焓对估算过量体积的影响。     

Simulation of mesoscale interfacial properties using the lattice Boltzmann method

We derive the mesoscopic interparticle potentials from macroscopic thermodynamics for van der Waals, Redlich-Kwong, and Redlich-Kwong-Soave equations of state and find that all these potentials are very similar to the Lennard-Jones potential. To in-vestigate the interfacial property at the mesoscale level, we incorporate free energy functions into the single-component multiphase lattice Boltzmann model and obtain the saturated density coexistence curves and interface mass density profiles across the interface using this method with different equations of state. The simulation results accurately reproduce the properties of equilibrium thermodynamics. Numerical results for single-component phase transitions indicate that a bubble-growth process is obtained and the equilibrium phase diagram is achieved at a given temperature. Bulk free energy, the interfacial energy coefficient, and other properties of nonequilibrium thermodynamic parameters, which are used to examine interfacial properties, are obtained in these simulations, and all these parameters are found to obey irreversible thermodynamics.     

P—T方程用于含夹带剂超临界流体相平衡的计算

将PT状态方程应用于固体溶质在含夹带剂超临外流体中的溶解度的计算。对溶质的物理性质、方程参数及二元交互作用参数的影响进行了较详细的讨论。在此基础上建立了一个新的立方型状态方程参数的混合规则,将该混合规则与PT状态方程相结合计算固体溶质在有无夹带剂超临界流体中的溶解度较采用传统的van der Waals混合规则计算的结果有较大改进。该混合规则在低压下溶质溶解度较低时可恢复到van der Waals混合规则。     

理论计算在GaN范德华异质结的光催化的研究进展

近年来,后石墨烯时代许多新型二维材料表现出优异的物理化学性能,同时以二维半导体材料为基础构建的二维范德华异质结复合材料为改善光催化剂性能开辟了新的研究方向。二维范德华异质结光催化剂可以增强对可见光的吸收和降低电子和空穴的复合,极大提升光催化性能。氮化镓（gallium nitride,GaN）材料具有禁带宽度大、电子漂移速度快、抗腐蚀性强和耐高温等优点,这为其作为半导体光催化剂提供了可能。介绍了光催化剂材料筛选和二维GaN基范德华异质结研究进展等,通过第一性原理密度泛函理论对二维GaN基异质结体系的光催化性质进行研究分析。     

用原子的X_α电荷密度计算van der Waals半径

利用原子的X_α电荷密度,在采用Norman规则选取原子球半径基础上,根据对大量分子中各原子Norman 半径的计算,提出一条确定原子在不同分子环境下Van der Waals 半径的简单经验公式.用此公式计算了18个常用原子在81个分子中的Van der Weals 半径,并对其物理意义进行了讨论.     

An optimization method for large van der Waals system

An optimization method for the geometry of large van der Waals system was suggested by discussing parallel dimer of benzene. The key of this method is to place some basis functions at interaction region of van der Waals molecules. It is possible to optimize large supramolecular system by using this method because it can greatly decrease the number of basis sets. This method was used to optimize the geometry of dimer of pyrene and the result is satisfactory.     

Van der Waals型流体相变问题的渐近稳定性

研究了van der Waals流体动力学方程组,通过引入人工黏性和周期边界条件,给出了此类流体方程组解的渐近稳定性。计算了带人工黏性的定常解问题,通过局部解的存在唯一性分析和先验估计,证明了定常解在全局范围内的渐近稳定性。     

一维Navier-Stokes-Cahn-Hilliard方程组解的适定性分析

讨论和描述了具有扩散界面的互不相溶气液两相流动的可压缩Navier-Stokes-Cahn-Hilliard（NSCH）方程组的周期边值问题，NSCH方程组中采用了van der Waals状态方程，该状态方程是关于密度非凸的刻画气液相变的经典模型。通过对压力的单调分解并结合能量估计的方法，克服了状态方程非凸性带来的困难，得到了流体密度的上下界估计；对任意初始值（密度不含真空），证明了该问题的一维流动强解是全局存在且唯一的。结果表明，该气液相变问题不会出现激波和真空现象。     

读《范德瓦耳斯气液状态方程纵横谈》的几点体会

对《范德瓦耳斯气液状态方程纵横谈》一文所涉及的几个问题进行了分析,指出了其不妥之处,并给出了正确的解释方法.     

蛋白质-核酸复合物中氢键和范德华力作用位点偏好性分析

对蛋白质-核酸复合物结构中氢键/范德华力作用位点氨基酸与核苷酸的偏好性(即相对使用频率)进行了统计分析.发现:(1)在蛋白质-DNA复合物结构中,范德华力作用对与氢键数量相当;而在蛋白质-RNA复合物结构中,范德华力作用对数量要远多于氢键;(2)复合物结构中氢键和范德华力作用位点上对氨基酸的偏好性差异显著;(3)氨基酸...     

A Functional Equation Governing the Motion of a Compressible Fluid Flow

Introduction　　In1952EberhardHopf[1]deducedadynamicalequationgoverningtheevolutionofthecharacteristicfunctionalofaturbulentvelocityfieldinanincompressiblefield,asaconsequenceoftheNavier-Stokesandcontinuityequations.Thepurposeofthispaperistostudythecasewhenthefluidiscompressible.Theword“fluid”denotesanyliquidorgaseousmedium,themostimportantdifferencebetweenthemechanicalpropertiesofliquidsandgasesliesintheirbulkelasticity,thatis,intheircompressibility.Gasescanbecompressedmuchmorethanliquids…     

对理想气体和范氏气体摩尔热容的再认识

讨论了理想气体和范德瓦耳斯气体的绝热过程，着重指出理想气体的摩尔热容比只在高温段可看作常量．而范德瓦耳斯气体的摩尔热容比即使在高温段也不可看作常量．     

甲醇水溶液中醋酸离解常数的理论计算

本文根据粒子间的相互作用力,导出了离解平衡常数的理论公式,并对醋酸在一系列浓度的甲醇水溶液中的离解平衡进行了理论计算.结果表明,本文所求得的 K_a 值要比由 Born 理论和 van derWaals 理论所求得的结果更符合实际.最后对这三个理论进行了简单的分析和讨论.     

N2-O2二聚物分子间相互作用势的第一性原理计算

原子间及分子间的范德瓦尔斯相互作用在分子结构和固体结构起着非常重要的作用. 在本文中,我们通过基于密度泛函理论的CPMD代码研究了氮气与氧气的分子间相互作用势, 所得结果与实验相符合. 在本工作中, 我们采用了最新且有效的范德瓦尔斯修正描述了至今还没有理论研究的氮气与氧气二聚物的分子间相互作用势.