Rodríguez-Rivas Álvaro, Galván José, Romero-Enrique José M
Departamento de Física Atómica, Molecular y Nuclear, Area de Física Teórica, Universidad de Sevilla, Apartado de Correos 1065, 41080 Sevilla, Spain.
J Phys Condens Matter. 2015 Jan 28;27(3):035101. doi: 10.1088/0953-8984/27/3/035101. Epub 2014 Dec 1.
We study the interfacial phenomenology of a fluid in contact with a one-dimensional array of infinitely long grooves of sinusoidal section, characterized by the periodicity length L and amplitude A. The system is modelled by the Landau-Ginzburg-Wilson functional, with fluid-substrate couplings which control the wettability of the substrate. We investigate the filling and wetting phenomena within the mean-field approximation, and compare with the predictions of the macroscopic and interfacial Hamiltonian theories. For large values of L and under bulk coexistence conditions, we observe first-order filling transitions between dry (D) and partially filled (F) interfacial states, and wetting transitions between partially filled F and completely wet (W) interfacial states of the same order as for the flat substrate. Depending on the order of the wetting transition, the transition temperature is either shifted towards lower temperatures for first-order wetting or it coincides with the wetting temperature on the flat substrate for continuous wetting. On the other hand, if the groove height is of order of the correlation length, only wetting transitions between D and W states are observed under bulk coexistence conditions. For this case, the transition temperature shift obeys approximately Wenzel's phenomenological law if the substrate favors first-order wetting, but it remains unshifted for continuous wetting. The borderline between the small and large L regimes correspond to a D - F - W triple point if wetting is first-order, and a D - F critical point for continuous wetting. Beyond bulk coexistence conditions, filling and first-order wetting transitions continue into off-coexistence filling and prewetting lines, which end up at critical points. Our findings show that the macroscopic theory only describes accurately the filling transition close to bulk coexistence and large L, while microscopic structure of the fluid is essential to understand wetting and filling away from bulk coexistence.
我们研究了一种流体与具有正弦截面的无限长凹槽的一维阵列接触时的界面现象学，其特征在于周期长度(L)和振幅(A)。该系统由朗道 - 金兹堡 - 威尔逊泛函建模，具有控制基底润湿性的流体 - 基底耦合。我们在平均场近似下研究填充和润湿现象，并与宏观和界面哈密顿理论的预测进行比较。对于较大的(L)值且在体共存条件下，我们观察到干（D）和部分填充（F）界面状态之间的一阶填充转变，以及部分填充的F和完全润湿（W）界面状态之间的润湿转变，其与平坦基底的情况具有相同的阶数。根据润湿转变的阶数，转变温度对于一阶润湿会向较低温度移动，或者对于连续润湿它与平坦基底上的润湿温度一致。另一方面，如果凹槽高度与关联长度相当，则在体共存条件下仅观察到D和W状态之间的润湿转变。对于这种情况，如果基底有利于一阶润湿，转变温度偏移大致遵循温泽尔现象学定律，但对于连续润湿它保持不变。如果润湿是一阶的，小(L)和大(L)区域之间的边界对应于一个D - F - W三相点，对于连续润湿则对应于一个D - F临界点。在体共存条件之外，填充和一阶润湿转变会延续到非共存填充和预湿线，这些线最终在临界点处结束。我们的研究结果表明，宏观理论仅能准确描述接近体共存和大(L)时的填充转变，而流体的微观结构对于理解远离体共存时的润湿和填充至关重要。
