Application of Free Energy Calculations at an Ultrahigh Temperature for Estimation of Molecular Diffusivities and Permeabilities in Zeolite Nanopores at an Ambient Temperature
详细信息 查看全文
- 作者：Ryo Nagumo ; Hiromitsu Takaba ; Shin-ichi Nakao
- 刊名：Journal of Physical Chemistry B
- 出版年：2009
- 出版时间：October 8, 2009
- 年：2009
- 卷：113
- 期：40
- 页码：13313-13321
- 全文大小：360K
- 年卷期：v.113,no.40(October 8, 2009)
- ISSN：1520-5207
文摘
Molecular diffusivities and gas permeabilities through zeolite nanopores, which have been difficult to simulate directly from conventional molecular dynamics (MD), were estimated at an ambient temperature by performing the free energy calculation at an ultrahigh temperature. In this method, the hopping rate of a guest molecule is calculated based on transition state theory. Using these hopping rates, molecular self-diffusivities for a CH4/CF4 binary mixture through an LTA-type zeolite, as well as those for each single component, are calculated at 300 K. The diffusivities of CF4 are in the order of ca. 10−14 m2/s at 300 K and thus are within an extremely slow molecular diffusion regime. Gas permeabilities of each single component at 300 K are also estimated by combining these calculated diffusivities with Fick’s first law. For predicting CH4 permeabilities, nonequilibrium MD is also applied for comparison, giving results within the same order, ca. 10−12 molm/m2sPa. This methodology dramatically reduces computational time when predicting molecular diffusivity and gas permeability.