Department of Chemical Engineering, Princeton University, Princeton, New Jersey 08544, USA.
J Chem Phys. 2010 Apr 14;132(14):144107. doi: 10.1063/1.3377089.
We perform histogram-reweighting grand canonical Monte Carlo simulations of the Lennard-Jones fluid confined between two parallel hard walls and determine the vapor-liquid critical and coexistence properties in the range of sigma<or=H<or=6sigma and 10sigma<or=L(x),L(y)<or=28sigma, where H is the wall separation, L(x)=L(y) is the system size and sigma is the characteristic length. By matching the probability distribution of the ordering operator, P(M), to the three-dimensional (3D) and two-dimensional (2D) Ising universality classes according to the mixed-field finite-size scaling approach, we establish a "phase diagram" in the (H,L) plane, showing the boundary between four types of behavior: 3D, quasi-3D, quasi-2D, and 2D. In order to facilitate 2D critical point calculation, we present a four-parameter analytical expression for the 2D Ising universal distribution. We show that the infinite-system-size critical points obtained by extrapolation from the apparent 3D and 2D critical points have only minor differences with each other. In agreement with recent reports in the literature [Jana et al., J. Chem. Phys. 130, 214707 (2009)], we find departure from linearity in the relationship between critical temperature and inverse wall separation, as well as nonmonotonic dependence of the critical density and the liquid density at coexistence upon wall separation. Additional studies of the ST2 model of water show similar behavior, which suggests that these are quite general properties of confined fluids.
我们对 Lennard-Jones 流体在两个平行硬壁之间的受限情况进行了直方图再加权巨正则蒙特卡罗模拟，并在 sigma<=H<=6sigma 和 10sigma<=L(x),L(y)<=28sigma 的范围内确定了汽液临界和共存性质，其中 H 是壁面分离，L(x)=L(y)是系统尺寸，sigma 是特征长度。通过根据混合场有限尺寸标度方法将有序算子 P(M)的概率分布与三维（3D）和二维（2D）Ising 普遍性类相匹配，我们在（H，L）平面上建立了一个“相图”，显示了四种行为之间的边界：3D、准 3D、准 2D 和 2D。为了方便二维临界点计算，我们提出了一个二维 Ising 普适分布的四参数解析表达式。我们表明，通过从明显的 3D 和 2D 临界点外推得到的无限系统尺寸临界点彼此之间只有很小的差异。与文献中的最近报道[Jana 等人，J. Chem. Phys. 130, 214707 (2009)]一致，我们发现临界温度与壁面分离的倒数之间的关系偏离线性，以及临界密度和共存时液体密度对壁面分离的非单调依赖性。对水的 ST2 模型的进一步研究表明了类似的行为，这表明这些是受限流体的相当普遍的性质。
