A new approach to the computation of entropy-related properties of fluids has been pre-sented.Application of the new technique to hard sphere fluids shows that it is capable of providingreliable estimates of such prop...A new approach to the computation of entropy-related properties of fluids has been pre-sented.Application of the new technique to hard sphere fluids shows that it is capable of providingreliable estimates of such properties as the chemical potential and Helmholtz free energy,even athigh density where other existing methods are hardly applicable.The chemical potential of an infinitedilute component in hard sphere systems has been estimated,and compared with that calculated fromthe Carnahan-Starling equation.展开更多
A local composition expression has been derived from the Guggenheim′s quasi-chemicalequation.On this basic a thermodynamic model,the quasi-chemical local composition model(QCLC)was established.To examine its capabili...A local composition expression has been derived from the Guggenheim′s quasi-chemicalequation.On this basic a thermodynamic model,the quasi-chemical local composition model(QCLC)was established.To examine its capability for correlation and prediction,Baxter′s adhesivehard sphere mixtures were used,and an improved numerical method was proposed to estimate theirthermodynamic properties.By means of this method the excess properties of the mixtures composedof four kinds of adhesive hard spheres were calculated,The activity coefficients from QCLC modelwere compared with those from the Wilson,NRTL and UNIQUAC equations.Results show thatamong these models,the QCLC model is the best one for correlation and prediction.展开更多
Three simple analytic expressions satisfying the limitation condition at low densities for the radial distribution function of hard spheres are developed in terms of a polynomial expansion of nonlinear base functions ...Three simple analytic expressions satisfying the limitation condition at low densities for the radial distribution function of hard spheres are developed in terms of a polynomial expansion of nonlinear base functions and the Carnahan-Starling equation of state. The simplicity and precision for these expressions are superior to the well-known Percus Yevick expression. The coefficients contained in these expressions have been determined by fitting the Monte Carlo data for the first coordination shell, and by fitting both the Monte Carlo data and the numerical results of PercusYevick expression for the second coordination shell. One of the expressions has been applied to develop an analytic equation of state for the square-well fluid, and the numerical results are in good agreement with the computer simulation data.展开更多
We present a simple method of obtaining various equations of state for hard sphere fluid in a simple unifying way. We will guess equations of state by using suitable axiomatic functional forms (n = 1, 2, 3, 4, 5) fo...We present a simple method of obtaining various equations of state for hard sphere fluid in a simple unifying way. We will guess equations of state by using suitable axiomatic functional forms (n = 1, 2, 3, 4, 5) for surface tension Sn (r), r≥ d/2 with intermolecular separation r as a variable, where m is an arbitrary real number (pole). Among the equations of state obtained in this way are Percus-Yevick, scaled particle theory and Carnahan-Starling equations of state. In addition, we have found a simple equation of state for the hard sphere fluid in the region that represents the simulation data accurately. It is found that for both hard sphere fluids as well as Lennard-Jones fluids, with m = 3/4 the derived equation of state (EOS) gives results which are in good agreement with computer simulation results. Furthermore, this equation of state gives the Percus-Yevick (pressure) EOS for the m = 0, the Carnahan-Starling EOS for rn = 4/5, while for the value of m = 1 it corresponds to a scaled particle theory EOS.展开更多
We discuss crystal formation in supersaturated suspensions of monodisperse hard spheres with a concentration of hard spheres randomly pinned in space and time. The pinning procedure introduces an external length scale...We discuss crystal formation in supersaturated suspensions of monodisperse hard spheres with a concentration of hard spheres randomly pinned in space and time. The pinning procedure introduces an external length scale and an external time scale that restrict the accessible number of configureurations and ultimately the number of pathways leading to crystallization. We observe a significant drop in the nucleation rate density at a characteristic pinning concentration that can be directly related to the structure of the critical nucleus and the dynamics of its formation in the unpinned system.展开更多
Covering a wide range of bulk densities, density profiles for hard-sphere chain fluids (HSCFs) with chain length of 3,4,8,20,32 and 64 confined between two surfaces were obtained by Monte Carlo simulations using exten...Covering a wide range of bulk densities, density profiles for hard-sphere chain fluids (HSCFs) with chain length of 3,4,8,20,32 and 64 confined between two surfaces were obtained by Monte Carlo simulations using extended continuum configurational-bias (ECCB) method. It is shown that the enrichment of beads near surfaces is happened at high densities due to the bulk packing effect, on the contrary, the depletion is revealed at low densities owing to the configurational entropic contribution. Comparisons with those calculated by density functional theory presented by Cai et al. indicate that the agreement between simulations and predictions is good. Compressibility factors of bulk HSCFs calculated using volume fractions at surfaces were also used to test the reliability of various equations of state of HSCFs by different authors.展开更多
The present work uses the concept of a scaled particle along with the perturbation and variation approach, to develop an equation of state (EOS) for a mixture of hard sphere (HS), Lennar-Jones (L J) fluids. A su...The present work uses the concept of a scaled particle along with the perturbation and variation approach, to develop an equation of state (EOS) for a mixture of hard sphere (HS), Lennar-Jones (L J) fluids. A suitable flexible functional form for the radial distribution function G(R) is assumed for the mixture, with R as a variable. The function G(R) has an arbitrary parameter m and a different equation of state can be obtained with a suitable choice of m. For m = 0.75 and m = 0.83 results are close to molecular dynamics (MD) result for pure HS and LJ fluid respectively.展开更多
Nanocrystalline diamond coatings were deposited by MPCVD on the spheres used for a ball bearing.The nanocrystalline coatings with a grain size of 50 nm were confirmed by the surface morphology and composition analysis...Nanocrystalline diamond coatings were deposited by MPCVD on the spheres used for a ball bearing.The nanocrystalline coatings with a grain size of 50 nm were confirmed by the surface morphology and composition analysis.The hardness of the coating is 20-40 GPa tested by nanoindentation,which is higher than that of tungsten carbide and silicon nitride substrates.The coating around the sphere observed from the Micro CT images is uniform with a thickness of 12 μm.展开更多
本文较为详细地介绍了自Van der Waals状态方程以来所发展的若干典型的状态方程,并对各类型的状态方程进行了评价。但到目前为止还没有一种状态方程能对任何物质在很大范围内都是通用的。特别对量子流体及某些强极性物质,任何状态方程...本文较为详细地介绍了自Van der Waals状态方程以来所发展的若干典型的状态方程,并对各类型的状态方程进行了评价。但到目前为止还没有一种状态方程能对任何物质在很大范围内都是通用的。特别对量子流体及某些强极性物质,任何状态方程都还有困难。当前的办法仍是将若干类状态方程同时并用,在不同场合选择最合适的方程使用。因此本文对于状态方程的详细的综述可以为工程设计及从事这方面研究的人员提供有价值的参考。展开更多
文摘A new approach to the computation of entropy-related properties of fluids has been pre-sented.Application of the new technique to hard sphere fluids shows that it is capable of providingreliable estimates of such properties as the chemical potential and Helmholtz free energy,even athigh density where other existing methods are hardly applicable.The chemical potential of an infinitedilute component in hard sphere systems has been estimated,and compared with that calculated fromthe Carnahan-Starling equation.
文摘A local composition expression has been derived from the Guggenheim′s quasi-chemicalequation.On this basic a thermodynamic model,the quasi-chemical local composition model(QCLC)was established.To examine its capability for correlation and prediction,Baxter′s adhesivehard sphere mixtures were used,and an improved numerical method was proposed to estimate theirthermodynamic properties.By means of this method the excess properties of the mixtures composedof four kinds of adhesive hard spheres were calculated,The activity coefficients from QCLC modelwere compared with those from the Wilson,NRTL and UNIQUAC equations.Results show thatamong these models,the QCLC model is the best one for correlation and prediction.
基金The project supported by National Natural Science Foundation of China under Grant Nos.19904002 and 10299040
by the Science and Technology Foundation for the Youth of the University of Electronic Science and Technology of China under Grant No.YF020703
文摘Three simple analytic expressions satisfying the limitation condition at low densities for the radial distribution function of hard spheres are developed in terms of a polynomial expansion of nonlinear base functions and the Carnahan-Starling equation of state. The simplicity and precision for these expressions are superior to the well-known Percus Yevick expression. The coefficients contained in these expressions have been determined by fitting the Monte Carlo data for the first coordination shell, and by fitting both the Monte Carlo data and the numerical results of PercusYevick expression for the second coordination shell. One of the expressions has been applied to develop an analytic equation of state for the square-well fluid, and the numerical results are in good agreement with the computer simulation data.
文摘We present a simple method of obtaining various equations of state for hard sphere fluid in a simple unifying way. We will guess equations of state by using suitable axiomatic functional forms (n = 1, 2, 3, 4, 5) for surface tension Sn (r), r≥ d/2 with intermolecular separation r as a variable, where m is an arbitrary real number (pole). Among the equations of state obtained in this way are Percus-Yevick, scaled particle theory and Carnahan-Starling equations of state. In addition, we have found a simple equation of state for the hard sphere fluid in the region that represents the simulation data accurately. It is found that for both hard sphere fluids as well as Lennard-Jones fluids, with m = 3/4 the derived equation of state (EOS) gives results which are in good agreement with computer simulation results. Furthermore, this equation of state gives the Percus-Yevick (pressure) EOS for the m = 0, the Carnahan-Starling EOS for rn = 4/5, while for the value of m = 1 it corresponds to a scaled particle theory EOS.
文摘We discuss crystal formation in supersaturated suspensions of monodisperse hard spheres with a concentration of hard spheres randomly pinned in space and time. The pinning procedure introduces an external length scale and an external time scale that restrict the accessible number of configureurations and ultimately the number of pathways leading to crystallization. We observe a significant drop in the nucleation rate density at a characteristic pinning concentration that can be directly related to the structure of the critical nucleus and the dynamics of its formation in the unpinned system.
基金Supported by the National Science Foundation of China (No. 29736170, No. 20025618) and the Doctoral Research Foundation by Ministry of Education of China (No. 1999025103). Additional support provided by the Visiting Researcher Foundation of University La
文摘Covering a wide range of bulk densities, density profiles for hard-sphere chain fluids (HSCFs) with chain length of 3,4,8,20,32 and 64 confined between two surfaces were obtained by Monte Carlo simulations using extended continuum configurational-bias (ECCB) method. It is shown that the enrichment of beads near surfaces is happened at high densities due to the bulk packing effect, on the contrary, the depletion is revealed at low densities owing to the configurational entropic contribution. Comparisons with those calculated by density functional theory presented by Cai et al. indicate that the agreement between simulations and predictions is good. Compressibility factors of bulk HSCFs calculated using volume fractions at surfaces were also used to test the reliability of various equations of state of HSCFs by different authors.
文摘The present work uses the concept of a scaled particle along with the perturbation and variation approach, to develop an equation of state (EOS) for a mixture of hard sphere (HS), Lennar-Jones (L J) fluids. A suitable flexible functional form for the radial distribution function G(R) is assumed for the mixture, with R as a variable. The function G(R) has an arbitrary parameter m and a different equation of state can be obtained with a suitable choice of m. For m = 0.75 and m = 0.83 results are close to molecular dynamics (MD) result for pure HS and LJ fluid respectively.
文摘Nanocrystalline diamond coatings were deposited by MPCVD on the spheres used for a ball bearing.The nanocrystalline coatings with a grain size of 50 nm were confirmed by the surface morphology and composition analysis.The hardness of the coating is 20-40 GPa tested by nanoindentation,which is higher than that of tungsten carbide and silicon nitride substrates.The coating around the sphere observed from the Micro CT images is uniform with a thickness of 12 μm.
文摘本文较为详细地介绍了自Van der Waals状态方程以来所发展的若干典型的状态方程,并对各类型的状态方程进行了评价。但到目前为止还没有一种状态方程能对任何物质在很大范围内都是通用的。特别对量子流体及某些强极性物质,任何状态方程都还有困难。当前的办法仍是将若干类状态方程同时并用,在不同场合选择最合适的方程使用。因此本文对于状态方程的详细的综述可以为工程设计及从事这方面研究的人员提供有价值的参考。