Department of Chemistry, College of Sciences, Persian Gulf University, Boushehr 75168, Iran.
Chemphyschem. 2013 Apr 2;14(5):1063-70. doi: 10.1002/cphc.201200873. Epub 2013 Feb 26.
A coarse-grained (CG) model for the simulation of nanoconfined water between graphene surfaces is developed. For this purpose, mixed-grained simulations are done, in which the two-site water model of Riniker and van Gunsteren [S. Riniker, W. F. van Gunsteren, J. Chem. Phys. 2011, 134, 084110] is simulated between atomistically resolved graphene surfaces. In the developed pure CG model, the two interaction sites of water and a combination of eight carbon atoms in the graphene surface are grouped together to construct water and surface CG beads. The pure CG potentials are constructed by iteratively matching the radial distribution functions and the density profiles of water beads in the pore with the corresponding mixed-grained distributions. The constructed potentials are shown to be pore-size transferable, capable of predicting structural properties of confined water over the whole range of pore sizes, ranging from extremely narrow pores to bulk water. The model is used to simulate a number of nanoconfined systems of a variety of pore sizes at constant temperature, constant parallel component of pressure, and constant surface area of the confining surfaces. The model is shown to predict the layering of water in contact with the surfaces, and the solvation force is in complete agreement with the mixed-grained model. It is shown that water molecules in the pore have smaller parallel diffusion coefficients compared to bulk water. Well-organized layers beside the surfaces are shown to have lower diffusion coefficients than diffuse layers. More information on the dynamics of water in the pore is obtained by calculating the rate of water exchange between slabs parallel to the surfaces. The time scale to achieve equilibrium for this process, depending on the pore width and on the degree of layering of water beside the surfaces, is a few nanoseconds in nanometric pores.
开发了一种用于模拟石墨烯表面之间纳米受限水的粗粒（CG）模型。为此，进行了混合粒模拟，其中模拟了 Riniker 和 van Gunsteren [S. Riniker，W. F. van Gunsteren，J. Chem. Phys. 2011，134，084110] 的双位点水分子模型在原子分辨的石墨烯表面之间。在开发的纯 CG 模型中，水分子的两个相互作用位点和石墨烯表面中的八个碳原子组合在一起，构建了水分子和表面 CG 珠。通过迭代匹配孔中水分子珠的径向分布函数和密度分布与相应的混合粒分布，构建了纯 CG 势。结果表明，所构建的势具有孔径可转移性，能够预测整个孔径范围内受限水的结构性质，从极窄的孔到体相水。该模型用于模拟各种孔径的许多纳米受限系统，在恒定温度、恒定平行压力分量和恒定约束表面面积下。结果表明，该模型预测了与表面接触的水的分层，溶剂化力与混合粒模型完全一致。结果表明，孔中水分子的平行扩散系数比体相水小。结果表明，与表面相邻的有序层的扩散系数比扩散层低。通过计算与表面平行的薄片之间的水交换速率，可以获得更多有关孔中水动力学的信息。对于这个过程达到平衡的时间尺度，取决于孔径和表面附近水的分层程度，在纳米级孔径中需要几纳秒。
