Stranski-Laboratorium für Physikalische und Theoretische Chemie, Fakultät für Mathematik und Naturwissenschaften, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany.
J Chem Phys. 2011 Nov 28;135(20):204702. doi: 10.1063/1.3660377.
We present grand canonical ensemble Monte Carlo simulations of prewetting transitions in a model liquid crystal at structureless solid substrates. Molecules of the liquid crystal interact via anisometric Lennard-Jones potentials and can be anchored planar or homeotropically at the substrates. Fluid-substrate attraction is modeled by a Yukawa potential of variable range. By monitoring the grand-potential density and the nematic order parameter as functions of the chemical potential μ, several discontinuous prewetting, wetting, and isotropic-nematic phase transitions are observed. These transitions depend on both the range of the fluid-substrate attraction and the specific anchoring at the substrate. Our results show that at substrates characterized by degenerate anchoring prewetting occurs at lower μ compared with cases in which the anchoring is monostable. This indicates that prewetting transitions are driven by orientational entropy because degenerate anchoring allows for more orientationally distinct configurations of molecules compared with monostable anchoring. In addition, by analyzing local density and various local order parameters, a detailed picture of the structure of various phases emerges from our simulations.
我们呈现了在无定形固体基底上的模型液晶预润湿转变的巨正则系综蒙特卡罗模拟。液晶分子通过各向异性 Lennard-Jones 势相互作用，并且可以在基底上平面或各向同性地锚定。流体-基底吸引力通过可变范围的 Yukawa 势来建模。通过监测巨势密度和向列序参量作为化学势 μ 的函数，可以观察到几个不连续的预润湿、润湿和各向同性-向列相转变。这些转变取决于流体-基底吸引力的范围和基底上的特定锚定。我们的结果表明，在具有退化锚定的基底上，与单稳态情况下相比，预润湿发生在较低的 μ 处。这表明预润湿转变是由取向熵驱动的，因为与单稳态锚定相比，退化锚定允许分子具有更多不同的取向构型。此外，通过分析局部密度和各种局部序参量，我们的模拟从各个方面详细地呈现了各个相的结构。
