Both a free volume approach for Helmholtz free energy and a theoretically-based fitted formula for radial distribution function (rdf) of hard sphere solid are employed to describe the Helmholtz free energy of Lennard-...Both a free volume approach for Helmholtz free energy and a theoretically-based fitted formula for radial distribution function (rdf) of hard sphere solid are employed to describe the Helmholtz free energy of Lennard-Jones solid in the framework of the first order thermodynamic perturbation theory, which also is employed for the uniform LennardJones fluid. The dividing of the Lennard-Jones potential follows from the WCA prescription, but the specification of the equivalent hard sphere diameter is determined by a simple iteration procedure devised originally for liquid state, but extended to solid state in the present study. Two hundred sheiks are used in the rdf to get an accurate perturbation term.The present approach is very accurate for the description of excess Helmholtz free energy of LJ solid, but shows some deviation from the simulation for excess Helmholtz free energy of uniform LJ fluid when the reduced temperature kT/ε is higher then 5. The present approach is satisfactory for description of solid-liquid phase transition of the Lennard-Jones model.展开更多
A new equation of self-diffusion coefficients for real fluids is proposed over wide temperature and density ranges.The new equation is derived from the molecular dynamics simulation data of LJ model fluid in literatur...A new equation of self-diffusion coefficients for real fluids is proposed over wide temperature and density ranges.The new equation is derived from the molecular dynamics simulation data of LJ model fluid in literature,which could be applied to gas,liquid and supercritical fluid (0≤ ρ * ≤1.0,0.8≤ T *≤4.0) with AAD 4.95% .With a generalized expression for the LJ parameters of pure real fluids according to the corresponding state principle and critical properties,the proposed equation is extended to pure real substances with the prediction accuracy 18.83%.Correlated LJ parameters are also used for comparison and the total AAD is 3.43% for 19 pure substances and 1299 data points.The new self-diffusion equation could be used in process design and development.展开更多
用7种有代表性物质在广域温度和压力范围内的液体物性实验值，对2个不同程度上修正的van der Waals模型进行比较和评价，结果表明，从统计力学出，进一步引入Lennard-Jones位能函数对内压项进行修正的 vaa der Waals模型，较仅对已占...用7种有代表性物质在广域温度和压力范围内的液体物性实验值，对2个不同程度上修正的van der Waals模型进行比较和评价，结果表明，从统计力学出，进一步引入Lennard-Jones位能函数对内压项进行修正的 vaa der Waals模型，较仅对已占体积项进行修正的van der Waals模型明显更优。展开更多
文摘Both a free volume approach for Helmholtz free energy and a theoretically-based fitted formula for radial distribution function (rdf) of hard sphere solid are employed to describe the Helmholtz free energy of Lennard-Jones solid in the framework of the first order thermodynamic perturbation theory, which also is employed for the uniform LennardJones fluid. The dividing of the Lennard-Jones potential follows from the WCA prescription, but the specification of the equivalent hard sphere diameter is determined by a simple iteration procedure devised originally for liquid state, but extended to solid state in the present study. Two hundred sheiks are used in the rdf to get an accurate perturbation term.The present approach is very accurate for the description of excess Helmholtz free energy of LJ solid, but shows some deviation from the simulation for excess Helmholtz free energy of uniform LJ fluid when the reduced temperature kT/ε is higher then 5. The present approach is satisfactory for description of solid-liquid phase transition of the Lennard-Jones model.
基金江苏省自然科学基金 (No .BK9712 4)国家杰出青年科学基金 (No .2 992 5 616)资助项目
文摘A new equation of self-diffusion coefficients for real fluids is proposed over wide temperature and density ranges.The new equation is derived from the molecular dynamics simulation data of LJ model fluid in literature,which could be applied to gas,liquid and supercritical fluid (0≤ ρ * ≤1.0,0.8≤ T *≤4.0) with AAD 4.95% .With a generalized expression for the LJ parameters of pure real fluids according to the corresponding state principle and critical properties,the proposed equation is extended to pure real substances with the prediction accuracy 18.83%.Correlated LJ parameters are also used for comparison and the total AAD is 3.43% for 19 pure substances and 1299 data points.The new self-diffusion equation could be used in process design and development.
文摘用7种有代表性物质在广域温度和压力范围内的液体物性实验值，对2个不同程度上修正的van der Waals模型进行比较和评价，结果表明，从统计力学出，进一步引入Lennard-Jones位能函数对内压项进行修正的 vaa der Waals模型，较仅对已占体积项进行修正的van der Waals模型明显更优。
