Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale A. Moro 2, 00185 Roma, Italy.
J Chem Phys. 2012 Aug 28;137(8):084704. doi: 10.1063/1.4746428.
We investigate the behavior of a patchy particle model close to a hard-wall via Monte Carlo simulation and density functional theory (DFT). Two DFT approaches, based on the homogeneous and inhomogeneous versions of Wertheim's first order perturbation theory for the association free energy are used. We evaluate, by simulation and theory, the equilibrium bulk phase diagram of the fluid and analyze the surface properties for two isochores, one of which is close to the liquid side of the gas-liquid coexistence curve. We find that the density profile near the wall crosses over from a typical high-temperature adsorption profile to a low-temperature desorption one, for the isochore close to coexistence. We relate this behavior to the properties of the bulk network liquid and find that the theoretical descriptions are reasonably accurate in this regime. At very low temperatures, however, an almost fully bonded network is formed, and the simulations reveal a second adsorption regime which is not captured by DFT. We trace this failure to the neglect of orientational correlations of the particles, which are found to exhibit surface induced orientational order in this regime.
我们通过蒙特卡罗模拟和密度泛函理论（DFT）研究了临近硬壁的斑粒子模型的行为。使用了两种基于均相和非均相 Wertheim 第一阶关联自由能微扰理论的 DFT 方法。我们通过模拟和理论评估了流体的平衡体相图，并分析了两个等压比的表面性质，其中一个等压比接近气液共存曲线的液相侧。我们发现，对于接近共存的等压比，壁附近的密度分布从典型的高温吸附分布转变为低温解吸分布。我们将这种行为与体相网络液体的性质联系起来，并发现理论描述在这个区域是相当准确的。然而，在非常低的温度下，几乎形成了一个完全键合的网络，模拟揭示了 DFT 无法捕捉的第二个吸附区域。我们将这种失败归因于对粒子的取向相关性的忽略，在这个区域中发现了表面诱导的取向有序。
