We consider a binary fluid mixture, which lies in the one-phase region near the demixing critical point. Short-range interactions between the mixture components and a solid surface in contact with the mixture can make the mixture composition inhomogeneous significantly near the surface. This inhomogeneity has been shown to cause various phenomena by using the renormalized local functional theory. In its free-energy density, the order-parameter field is coarse-grained without rescaled and only the most singular part is specified. In the present study, on the basis of the crossover theory, we introduce a square-gradient term to the free-energy density of the extended non-random two-liquid model, which includes more than the most singular part. Thanks to similarity between the renormalized local functional theory and the crossover theory, the relationship between the two free-energy densities can be clarified. Supposing a mixture of nitroethane and 3-methylpentane and a mixture of 2,6-lutidine and water, we use the proposed free-energy density to calculate the inhomogeneous composition profile numerically. The free-energy density also enables us to calculate excess densities of entropy and enthalpy, unlike that of the renormalized local functional theory. We also find that the magnitude of the thermal force density, which is induced by a temperature gradient to cause flow in thermoosmosis, can depend on the calculation procedures significantly.

中文翻译：

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在非随机双液模型框架中分析近临界二元流体混合物中的优先吸附

我们考虑二元流体混合物，它位于分层临界点附近的单相区域。混合物组分和与混合物接触的固体表面之间的短程相互作用可以使混合物组成在表面附近显着不均匀。通过使用重正化局部泛函理论，这种不均匀性已被证明会导致各种现象。在其自由能密度中，有序参数场是粗粒度的，无需重新缩放，并且仅指定最奇异的部分。在本研究中，基于交叉理论，我们将平方梯度项引入到扩展非随机二液模型的自由能密度中，该模型包含的不仅仅是最奇异的部分。由于重正化局域泛函理论与交叉理论之间的相似性，可以阐明两个自由能密度之间的关系。假设硝基乙烷和 3-甲基戊烷的混合物以及 2,6-二甲基吡啶和水的混合物，我们使用所提出的自由能密度来数值计算不均匀成分分布。与重正化局部泛函理论不同，自由能密度还使我们能够计算熵和焓的过剩密度。我们还发现，由温度梯度引起的热渗透流动的热力密度的大小可以显着取决于计算程序。