Determination of adsorption equilibria in pores by molecular dynamics in a unit cell with imaginary gas phase
Determination of adsorption equilibria in pores by molecular dynamics in a unit cell with imaginary gas phase
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假想气相晶胞中分子动力学测定孔隙中的吸附平衡
DOI：
10.1063/1.473801
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发表时间：
1997
影响因子：
4.4
通讯作者：
M. Okazaki
中科院分区：
文献类型：
--
作者：
M. Miyahara;Tomohisa Yoshioka;M. Okazaki
我们发展了一个新的分子动力学（MD）计划，引入潜在的缓冲场的概念，通过它吸附相可以与一个虚构的气相相互作用。这个模拟单元允许我们进行MD模拟，允许改变分子数量以在给定的平衡压力下达到平衡，就像巨正则蒙特卡罗模拟一样。通过对池的设置进行另一种选择，分子的数量保持恒定，但平衡压力能够通过“粒子计数法”的新技术容易地获得。由此得到的平衡汽相压力与Widom的粒子插入法得到的结果一致。在2和3 nm的狭缝状孔内进行了一些吸附模拟。吸附现象可以从低相对压力下的孔壁单层吸附到高相对压力下的毛细凝聚。从而确定了吸附平衡关系式。毛细冷凝的临界相对压力小于修正Kelvin方程的预测值。该方法在界面研究方面具有很大的优势，对分析孔隙中的凝结水具有重要意义。
We developed a new molecular dynamics (MD) scheme, introducing the concept of the potential buffering field through which an adsorbed phase could interact with an imaginary gas phase. This simulation cell allowed us to conduct a MD simulation that allowed a change in the number of molecules to attain equilibrium with given equilibrium pressure, like a grand canonical Monte Carlo simulation. By taking another choice for the setting of the cell, the number of molecules stayed constant but the equilibrium pressure was able to be obtained easily by a new technique of “particle counting method.” The thus obtained equilibrium vapor-phase pressure agreed with that obtained by Widom’s particle insertion method. Some adsorption simulations within slitlike pores of 2 and 3 nm were carried out. Adsorption phenomena could be observed from monolayeradsorption on a pore wall under a low relative pressure to the capillary condensation under a high relative pressure. Thus the adsorption equilibrium relation could be determined. The critical relative pressure for capillary condensation was smaller than that predicted by the modified Kelvin equation. This MD method shall provide much benefit in studying interfaces, which is important for analyzing condensation in pores.