共查询到20条相似文献,搜索用时 968 毫秒
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使用非平衡分子动力学模拟方法研究了单原子LJ流体的非牛顿流变行为,并在系统中分别施加稳态Couette流场和振荡剪切流场.在Couette流场的模拟中,流体出现剪切变稀和法向应力差效应,不同剪切率下的径向分布函数反映了流体分子由于剪切所导致的微观结构变化,通过分析势能函数发现当剪切率增大时,分子间排斥作用增强,吸引作用减弱.在振荡剪切流场的模拟中,发现剪切应力和剪切率之间的相位差随频率增加而增加,随频率增加复数粘度的实部先增大再减小,虚部单调增加,导致虚部粘度相对实部粘度比例增大,弹性模量和粘性模量之比也随频率增加而增加.这三点现象表明LJ流体出现粘弹性行为,且在高频率下,弹性所占比重增大. 相似文献
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根据所得到Kr HF体系的两种弱结合分子的结构参数、离解能和谐性力常数 ,采用多体项展式方法 ,对Kr HF体系的性质和势能函数重新进行了研究。导出KrHF(X1Σ+)基态分子的分析势能函数 ,获得KrHF(X1Σ+)体系的势能面。考察了这个势能函数的基本性质 ,准确地复现出Kr HF分子的平衡结构特征 相似文献
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确定了面心立方晶格中线性分子的障碍转动势能函数形式,基于光谱数据中导出惰性气体晶格中的HF分子的障碍传动势能函数。 相似文献
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采用从头计算的多参考组态CI方法(MRCI) 和B原子Dunnings相关调和基函数含扩散基的大基组aug-cc-pVQZ对B+2分子的基态和低激发态的势能曲线进行计算 .利用Huxley函数、Murrell-Sorbie函数和最小二乘法拟合出了解析势能函数,并以此为基础计算出光谱常数.通过比较发现:Huxley 函数比MS函数的拟合方差更小,能更好地再现分子中原子间相互作用.采用两种函数所得解析势能函数与从头计算势能曲线间的误差RMS 均远小于化学精度4.184 kJ/mol的要求,表明所得解析势能函数很好地再现了这些态中原子间的相互作用情况,可用于更广泛的研究. 相似文献
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本文所导出的22个基态双原子分子HFACE势能函数,都具有正确的平衡性质和长程Van der Waals区域正确的渐近性质,表示了完整正确的分子势能曲线。 相似文献
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陈明伦 《原子与分子物理学报》2007,24(Z1):51-52
运用原子分子群表示方法,首先确定NaLi分子的电子基态(X1∑ ).然后选用6-311 G(3df,2pd)基组优化计算得到NaLi分子基态(X1∑ )的平衡结构和离解能,采用电子相关QCISD(T)方法结合6-311 G(3df,2pd)基组对NaLi分子基态进行单点能扫描计算.最后用单点扫描计算值结合优化计算所得参数去拟合Murrell-Sorbie函数,得到了NaLi分子基态的势能函数.用该势能函数计算的光谱常数与实验结果符合得很好,表明拟合确定的势能函数能精确地描述基态NaLi分子的结构和性质. 相似文献
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Canales M Padró JA 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》1999,60(1):551-558
The dependence of the dynamic properties of liquid metals and Lennard-Jones fluids on the characteristics of the interaction potentials is analyzed. Molecular-dynamics simulations of liquids in analogous conditions but assuming that their particles interact either through a Lennard-Jones or a liquid-metal potential were carried out. The Lennard-Jones potentials were chosen so that both the effective size of the particles and the depth of the potential well were very close to those of the liquid-metal potentials. In order to investigate the extent to which the dynamic properties of liquids depend on the short-range attractive interactions as well as on the softness of the potential cores, molecular-dynamics simulations of the same systems but assuming purely repulsive interactions with the same potential cores were also performed. The study includes both single-particle dynamic properties, such as the velocity autocorrelation functions, and collective dynamic properties, such as the intermediate scattering functions, the dynamic structure factors, the longitudinal and transverse current correlations, and the transport coefficients. 相似文献
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N. Faginas Lago F. Huarte Larra?aga M. Albertí 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(1):75-85
Energetic and structural properties of liquid water have been calculated using molecular dynamics simulations in order to
investigate the effect of different formulations of the van der Waals (vdW) interaction on the behaviour of liquid water.
In particular, two model potentials, the SPC/E using a Lennard Jones (LJ) function and the AMPF using an Improved Lennard
Jones function (ILJ) have been considered. The flexibility of the ILJ function in the AMPF model has also been analysed, proving
that its vdW component can match different parametrizations of the electrostatic component. 相似文献
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The volume pinning force in superconductors with randomly distributed line defects nearly perpendicular to the flux lines is calculated for model as well as realistic interaction potentials between single defects and single flux lines. Both attractive and repulsive interactions defect — flux line were considered. The line defects were constructed from point defects distributed with constant density on straight lines. The deviations of the results from the theory of Labusch are considerable for small elementary interaction forces between defects and flux lines. The deviations (as well as the differences between repulsive and attractive interaction potentials) are larger for the realistic interaction potential than those for the different model potentials. The threshold values for the flux line distortion (under which no net volume pinning can exist) is also given. 相似文献
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The influence of dispersive long-range interactions on properties of vapour–liquid equilibria and interfaces of six binary Lennard-Jones (LJ) mixtures was studied by molecular dynamics (MD) simulations and density gradient theory (DGT). The mixtures were investigated at a constant temperature T, at which the low-boiling component, which is the same in all mixtures, is subcritical. Two different high-boiling components were considered: one is subcritical, the other is supercritical at T. Furthermore, the unlike dispersive interaction was varied such that mixtures with three different types of phase behaviour were obtained: ideal, low-boiling azeotrope, and high-boiling azeotrope. In a first series of simulations, the full LJ potential was used to describe these mixtures. To assess the influence of the long-range interactions, these results were compared with simulations carried out with the LJ truncated and shifted (LJTS) potential applying the corresponding states principle. The dispersive long-range interactions have a significant influence on the surface tension and the interfacial thickness of the studied mixtures, whereas the relative adsorption and the enrichment are hardly affected. Furthermore, the influence of the long-range interactions on Henry's law constants and the phase envelopes of the vapour–liquid equilibrium was investigated. The long-range interactions have practically no influence on the composition dependency of the investigated mixture properties. 相似文献
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P Domínguez-García 《The European physical journal. E, Soft matter》2012,35(8):9752-10
By using microrheological methods commonly employed in videomicroscopy experiments, we study the rheology of a two-dimensional computational fluid formed by Brownian disks with the aim of exploring the influence of some effective colloid-colloid attractive interactions. The model of fluid is developed by Brownian dynamics simulations without hydrodynamical interactions, and it is characterized by calculating its equation of state from the pair distribution function. Micromechanical properties, relative and intrinsic viscosity and freezing are discussed. Then, we include attractive forces such a Asakura-Oosawa depletion force or an empiric expression proposed by Grier and Hal (GH) for an anomalous electrostatic potential observed in confined and charged colloids. By using both potentials, viscosity is clearly increased, but when the GH potential is included, viscoelastic gel state is reached for intermediate values of surface concentration. Finally, we analyse the influence of the attractive potentials in the breaking-up by thermal fluctuations of linear chains formed by 2D particles, finding that the GH potential reduces the characteristical time at which the disks can be considered as disaggregated. In this work, we employ an experimental-like methodology for the study of a Brownian hard-disk fluid, providing a very useful link with experimental procedures. 相似文献
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利用自由能方法的分子动力学模拟,计算了零压下Al的熔化温度.在计算液相自由能的过程中,采用勒纳-琼斯(LJ)液体作为参考系统,同时将计算结果与Mei和Davenport等人的计算结果进行了比较,计算结果表明:1)选用LJ参考系统使液相自由能的计算时间节省一半,并且不影响熔化温度的计算结果;2)采用不同的埋入原子势(EAM)的分子动力学模拟计算得到的熔化温度与实验值都存在偏差,而就金属Al而言,采用Cai等人的EAM势的熔化温度的计算结果比Mei和Davenport及Morris等人采用的势模型的结果略有改
关键词:
熔化温度
自由能方法
分子动力学模拟 相似文献
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Influence of polymer-pore interactions on translocation 总被引:1,自引:0,他引:1
We investigate the influence of polymer-pore interactions on the translocation dynamics using Langevin dynamics simulations. An attractive interaction can greatly improve the translocation probability. At the same time, it also increases the translocation time slowly for a weak attraction while an exponential dependence is observed for a strong attraction. For fixed driving force and chain length the histogram of translocation time has a transition from Gaussian distribution to long-tailed distribution with increasing attraction. Under a weak driving force and a strong attractive force, both the translocation time and the residence time in the pore show a nonmonotonic behavior as a function of the chain length. Our simulations results are in good agreement with recent experimental data. 相似文献
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Carlos Handrey Araujo Ferraz 《Physics letters. A》2019,383(31):125884
In this paper, we perform molecular dynamics (MD) simulations to study the random packing of spheres with different particle size distributions. In particular, we deal with non-Gaussian distributions by means of the Lévy distributions. The initial positions as well as the radii of five thousand non-overlapping particles are assigned inside a confining rectangular box. After that, the system is allowed to settle under gravity towards the bottom of the box. Both the translational and rotational movements of each particle are considered in the simulations. In order to deal with interacting particles, we take into account both the contact and long-range cohesive forces. The normal viscoelastic force is calculated according to the nonlinear Hertz model, whereas the tangential force is calculated through an accurate nonlinear-spring model. Assuming a molecular approach, we account for the long-range cohesive forces using a Lennard-Jones (LJ)-like potential. The packing processes are studied assuming different long-range interaction strengths. 相似文献
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Mariana Köber Enrique Sahagún Martina Fuss Fernando Briones Mónica Luna Juan José Sáenz 《固体物理学:研究快报》2008,2(3):138-140
The effects of adhesion hysteresis in the dynamic‐dissipation curves measured in amplitude‐modulation atomic force microscopy are discussed. Hysteresis in the interaction forces is shown to modify the dynamics of the cantilever leading to different power dissipation curves in the repulsive and attractive regimes. Experimental results together with numerical simulations show that power dissipation, as measured in force microscopy, is not always proportional to the energy dissipated in the tip–sample interaction process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The delocalization and unbinding transitions of two semi-flexible polymers which experience attractive interactions are studied
by a variety of theoretical methods. In two-dimensional systems, one has to distinguish four different universality classes
for the interaction potentials. In particular, the delocalization transitions from a potential well and the unbinding transitions
from such a well in the presence of a hard wall exhibit distinct critical behavior governed by different critical exponents.
In three-dimensional systems, we predict first-order transitions with a jump in the energy density but with critical or self-similar
fluctuations leading to distribution functions with power law tails. The predicted critical behavior is confirmed numerically
by transfer matrix calculations in two dimensions and by Monte Carlo simulations in three dimensions. This behavior should
be accessible to experiments on biopolymers such as actin filaments or microtubuli.
Received 15 December 1999 and Received in final form 19 May 2000 相似文献