物理化学学报 >> 2003, Vol. 19 >> Issue (06): 538-542.doi: 10.3866/PKU.WHXB20030612

研究论文 上一篇    下一篇

密度泛函与分子模拟计算介孔孔径分布比较

邵晓红;张现仁;汪文川   

  1. 北京化工大学化学工程学院,北京　100029
  • 收稿日期:2002-10-24 修回日期:2003-01-14 发布日期:2003-06-15
  • 通讯作者: 汪文川 E-mail:wchwang@163bj.com

Comparison of Density Functional Theory and Molecular Simulation Methods for Pore Size Distribution of Mesoporous Materials

Shao Xiao-Hong;Zhang Xian-Ren;Wang Wen-Chuan   

  1. College of Chemical Engineering,Beijing University of Chemical and Technology,Beijing　100029
  • Received:2002-10-24 Revised:2003-01-14 Published:2003-06-15
  • Contact: Wang Wen-Chuan E-mail:wchwang@163bj.com

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摘要： 用巨正则系综Monte Carlo模拟(GCMC)方法和密度泛函理论（ DFT）结合统计积分方程（SIE）计算了介孔材料的孔径分布.为比较这两种方法,以77 K氮气在介孔活性碳微球中的吸附数据为依据,求出其孔径分布.在GCMC模拟和DFT计算中,流体分子模型化为单点的Lerrnard-Jones球;流体分子与吸附剂材料之间的作用采用平均场理论中的10-4-3模型.在DFT方法中,自由能采用Tarazona 提出的加权近似密度泛函方法(weighted density approximation,WDA)求解.结果表明,对于孔径大于1.125 nm的介孔材料,GCMC和DFT两种方法都可以用来研究介孔材料的孔径分布;对于小于1.125 nm的介孔材料,不能用DFT方法计算孔径分布（DFT方法本身的近似产生了误差）,只能用分子模拟方法.

关键词: 巨正则系综Monte Carlo方法, 密度泛函理论, 孔径分布, 吸附

Abstract: The pore size distribution(PSD) is the major characteristics of the heterogeneity for the mesoporous materials.Together with statistics integral equation,two methods,grand canonical Monte Carlo(GCMC)method and density functional theory(DFT),are used to study the PSD of mesoporous materials.In order to compare the two methods,the PSD of activated meso-carbon microbeads( a-MCMBs) is calculated based on the nitrogen adsorption isotherm at 77 K.In GCMC simulation and DFT calculation,the nitrogen is modeled as a Lennord-Jones (LJ)spherical molecule.The well-known steele's 10-4-3 potential is used to represent the interaction between the fluid molecule and the solid wall.The weighted density approximation of Tarazona's theory is used to get the free energy.The PSDs for the mesoporous material predicted by the two methods are in good line for larger pore sizes(larger than 1.125 nm),while for small pore sizes,DFT deviates significantly due to inherent approximations.

Key words: Grand canonical Monte Carlo method, Density functional theory, Pore size distribution, Adsorption