Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, Ontario, Canada.
J Chem Phys. 2010 Dec 14;133(22):224703. doi: 10.1063/1.3505453.
Grand canonical Monte Carlo simulations are used to examine the adsorption and structure of water in the interior of cylindrical nanopores in which the axial symmetry is broken either by varying the radius as a function of position along the pore axis or by introducing regions where the characteristic strength of the water-nanopore interaction is reduced. Using the extended simple point charge (SPC∕E) model for water, nanopores with a uniform radius of 6.0 Å are found to fill with water at chemical potentials approximately 0.5 kJ∕mol higher than the chemical potential of the saturated vapor. The water in these filled pores exists in either a weakly structured fluidlike state or a highly structured uniformly polarized state composed of a series of stacked water clusters with pentagonal cross sections. This highly structured state can be disrupted by creating hydrophobic regions on the surface of the nanopore, and the degree of disruption can be systematically controlled by adjusting the size of the hydrophobic regions. In particular, hydrophobic banded regions with lengths larger than 9.2 Å result in a complete loss of structure and the formation of a liquid-vapor coexistence in the tube interior. Similarly, the introduction of spatial variation in the nanopore radius can produce two condensation transitions at distinct points along the filling isotherm.
巨正则蒙特卡罗模拟被用来研究水在圆柱纳米孔内部的吸附和结构，这些纳米孔的轴对称性被破坏，一种方式是沿孔轴的位置变化半径，另一种方式是引入特征强度降低的纳米孔-水相互作用区域。使用扩展的简单点电荷（SPC∕E）水模型，发现具有均匀半径 6.0 Å 的纳米孔在化学势约比饱和蒸气化学势高 0.5 kJ∕mol 的条件下充满水。这些充满水的孔中的水要么处于弱结构的流体状态，要么处于高度结构的均匀极化状态，由一系列堆叠的具有五边形横截面的水团簇组成。通过在纳米孔表面上创建疏水区，可以破坏这种高度结构化的状态，并且可以通过调整疏水区的大小来系统地控制破坏的程度。特别地，长度大于 9.2 Å 的疏水区带会导致管内结构完全丧失，形成液体-蒸气共存。同样，纳米孔半径的空间变化可以在填充等温线的不同点产生两个冷凝转变。
