Drying and wetting transitions of a Lennard-Jones fluid: Simulations and density functional theory.
Drying and wetting transitions of a Lennard-Jones fluid: Simulations and density functional theory.
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DOI：
10.1063/1.4993515
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发表时间：
2017-05
期刊：
影响因子：
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通讯作者：
R. Evans;M. C. Stewart;N. Wilding
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文献类型：
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作者：
R. Evans;M. C. Stewart;N. Wilding
我们报告了截断的伦纳德-琼斯流体在平坦无结构壁上的干燥和润湿相变的理论和模拟研究。结合势计算预测，这些转变的性质取决于壁流体吸引力是否具有长程（LR）幂律衰减，或者被截断，使其呈现短程（SR）。使用大正则蒙特卡罗模拟和经典密度泛函理论，我们详细研究了这两种情况。我们发现，对于 LR 情况，润湿是一阶的，而干燥是连续的（临界的）并且恰好发生在零吸引力壁强度下，即在硬壁的极限内。在 SR 情况下，干燥也很关键，但润湿转变的顺序取决于壁流体势的截断范围。我们根据密度和局部压缩性曲线以及通过整体密度概率分布的有限尺寸缩放特性来描述临界干燥和润湿的方法。对于 LR 情况，干燥点已知，该分析使我们能够估计指数 ν∥，它控制平行相关长度，即壁上气泡的范围。令人惊讶的是，我们获得的值是平均场和重正化群计算预测的两倍多，尽管我们的三维系统处于临界指数平均场理论预计成立的上临界维度。根据对近临界有限尺寸效应性质的新见解，讨论了造成这种差异的可能原因。
We report a theoretical and simulation study of the drying and wetting phase transitions of a truncated Lennard-Jones fluid at a flat structureless wall. Binding potential calculations predict that the nature of these transitions depends on whether the wall-fluid attraction has a long ranged (LR) power law decay or is instead truncated, rendering it short ranged (SR). Using grand canonical Monte Carlo simulation and classical density functional theory, we examine both cases in detail. We find that for the LR case wetting is first order, while drying is continuous (critical) and occurs exactly at zero attractive wall strength, i.e., in the limit of a hard wall. In the SR case, drying is also critical but the order of the wetting transition depends on the truncation range of the wall-fluid potential. We characterize the approach to critical drying and wetting in terms of the density and local compressibility profiles and via the finite-size scaling properties of the probability distribution of the overall density. For the LR case, where the drying point is known exactly, this analysis allows us to estimate the exponent ν∥, which controls the parallel correlation length, i.e., the extent of vapor bubbles at the wall. Surprisingly, the value we obtain is over twice that predicted by mean field and renormalization group calculations, despite the fact that our three dimensional system is at the upper critical dimension where mean field theory for critical exponents is expected to hold. Possible reasons for this discrepancy are discussed in the light of fresh insights into the nature of near critical finite-size effects.