Both the grand canonical Monte Carlo and molecular dynamics simulation methods are used to investigate the adsorption and diffusion of carbon dioxide confined in a 1.86 nm slit carbon pore at 4 temperatures from subcr...Both the grand canonical Monte Carlo and molecular dynamics simulation methods are used to investigate the adsorption and diffusion of carbon dioxide confined in a 1.86 nm slit carbon pore at 4 temperatures from subcritical (120 K) to supercritical (313 K) conditions. Layering transition, capillary condensation and adsorption hysteresis are found at 120 K. The microstructure of carbon dioxide fluid in the slit carbon pore is analyzed. The diffusion coefficients of carbon dioxide parallel to the slit wall are significantly larger than those normal to the slit wall.展开更多
Assuming the pores in a porous solid to be slit-shaped,according to the principle of surface chemical thermody-namics,an equation for the calculation of pore size fromthe desorption branch of the isotherm of physical ...Assuming the pores in a porous solid to be slit-shaped,according to the principle of surface chemical thermody-namics,an equation for the calculation of pore size fromthe desorption branch of the isotherm of physical adsorp-tion of nitrogen on the porous solid at liquid nitrogentemperature is derived.The calculation results obtainedby different methods,namely,the classical method,BBmethod and the method of this paper,are compared.Comparison shows that the pore sizes d_T and d_H calculat-ed by the method of this paper and BB method respec-tively are larger than the pore size d_c calculated by theclassical method in the range 0【p/p_s【1;d_T】d_Hatp/p_s【0.71 and d_H】d_T at p/p_s】0.71;The results byBB method and the method of this paper tend to be thesame as that by the classical method while p/p_s ap-proaches 1.展开更多
The paper presents a Monte Carlo simulation to study the adsorption characteristics of methane molecule on coal slit pores from different aspects.Firstly,a physical model of adsorption and desorption of methane molecu...The paper presents a Monte Carlo simulation to study the adsorption characteristics of methane molecule on coal slit pores from different aspects.Firstly,a physical model of adsorption and desorption of methane molecules on micropores was established.Secondly,a grand canonical ensemble was introduced as the Monte Carlo simulation system.Thirdly,based on the model and system,the molecule simulation program was developed with VC++6.0 to simulate the isothermal adsorption relationship between the amount of molecule absorption and the factors affecting it.Lastly,the numerically simulated results were compared with measured results of adsorption coal samples of two different coal mines with a laboratory gas absorption instrument.The results show that the molecule simulations of the adsorption constants,the adsorption quantity,and the isothermal adsorption curve at the same and different coal temperatures were in good agreement with those measured in the experiments,indicating that it is feasible to use the established model and the Monte Carlo molecule simulation to study the adsorption characteristics of methane molecules in coal.展开更多
A density functional theory is applied to calculating the local density profiles of colloids confined in a slit-like pore as well as the radial distribution functions of bulk colloids. The interaction between the coll...A density functional theory is applied to calculating the local density profiles of colloids confined in a slit-like pore as well as the radial distribution functions of bulk colloids. The interaction between the colloidal particles is described using a hard-core Yukawa model. The excess Helmholtz energy functional is a combination of the modified fundamental measure theory of Yu and Wu （2002） for the hard-core contribution and a corrected mean-field theory for the attractive contribution. Comparison with the results from the Monte Carlo simulations shows that the corrected theory improves the density profiles of colloids in the vicinity of contact over the original mean-field theory. Both the present corrected theory and simulations suggest that there are depletion and desorption for the colloid with strong attraction between particles at low temperature.展开更多
基金Supported by the State Key Fundamental Research Plan of China (No. G2000048010) and National High Performance Computing Foundation of China (No. 99118).
文摘Both the grand canonical Monte Carlo and molecular dynamics simulation methods are used to investigate the adsorption and diffusion of carbon dioxide confined in a 1.86 nm slit carbon pore at 4 temperatures from subcritical (120 K) to supercritical (313 K) conditions. Layering transition, capillary condensation and adsorption hysteresis are found at 120 K. The microstructure of carbon dioxide fluid in the slit carbon pore is analyzed. The diffusion coefficients of carbon dioxide parallel to the slit wall are significantly larger than those normal to the slit wall.
文摘Assuming the pores in a porous solid to be slit-shaped,according to the principle of surface chemical thermody-namics,an equation for the calculation of pore size fromthe desorption branch of the isotherm of physical adsorp-tion of nitrogen on the porous solid at liquid nitrogentemperature is derived.The calculation results obtainedby different methods,namely,the classical method,BBmethod and the method of this paper,are compared.Comparison shows that the pore sizes d_T and d_H calculat-ed by the method of this paper and BB method respec-tively are larger than the pore size d_c calculated by theclassical method in the range 0【p/p_s【1;d_T】d_Hatp/p_s【0.71 and d_H】d_T at p/p_s】0.71;The results byBB method and the method of this paper tend to be thesame as that by the classical method while p/p_s ap-proaches 1.
基金supported by the Industrial Research Project in Guizhou Science and Technology Bureau of China (GY(2011)No.3012)International Cooperation Projects in Guizhou Science and Technology Bureau of China (G(2009)No.700111)
文摘The paper presents a Monte Carlo simulation to study the adsorption characteristics of methane molecule on coal slit pores from different aspects.Firstly,a physical model of adsorption and desorption of methane molecules on micropores was established.Secondly,a grand canonical ensemble was introduced as the Monte Carlo simulation system.Thirdly,based on the model and system,the molecule simulation program was developed with VC++6.0 to simulate the isothermal adsorption relationship between the amount of molecule absorption and the factors affecting it.Lastly,the numerically simulated results were compared with measured results of adsorption coal samples of two different coal mines with a laboratory gas absorption instrument.The results show that the molecule simulations of the adsorption constants,the adsorption quantity,and the isothermal adsorption curve at the same and different coal temperatures were in good agreement with those measured in the experiments,indicating that it is feasible to use the established model and the Monte Carlo molecule simulation to study the adsorption characteristics of methane molecules in coal.
基金This work is sponsored by the National Natural Science Foun’ dation of China(Grant No．20376037) the National Basic Research Pr0gram of China(Grant No．2003CB61 5700)
文摘A density functional theory is applied to calculating the local density profiles of colloids confined in a slit-like pore as well as the radial distribution functions of bulk colloids. The interaction between the colloidal particles is described using a hard-core Yukawa model. The excess Helmholtz energy functional is a combination of the modified fundamental measure theory of Yu and Wu （2002） for the hard-core contribution and a corrected mean-field theory for the attractive contribution. Comparison with the results from the Monte Carlo simulations shows that the corrected theory improves the density profiles of colloids in the vicinity of contact over the original mean-field theory. Both the present corrected theory and simulations suggest that there are depletion and desorption for the colloid with strong attraction between particles at low temperature.
