Molecular dynamics simulations were carried out to investigate cylindrical droplets consisting of binary mixtures of Lennard-Jones (LJ) fluids in contact with a solid substrate. The droplets are composed of mixtures of the monomeric LJ fluid plus linear-tangent chains of 2, 10, 20, and 30 segments per chain that interact through a harmonic potential and the spherically truncated and shifted potential Lennard-Jones. The solid surface was modeled as a semi-infinite platinum substrate with an FCC structure that interacts with the fluid by means of a LJ 9-3 potential. We place emphasis on the effect of mixing a monomeric LJ fluid with heavy components on the contact angle and on the droplet structure, especially in the liquid–solid region. The density profiles of the droplets reveal a strong discrete layering of the fluid in the vicinity of the solid–liquid interface. The layering is more pronounced at low temperatures and for mixtures of short chains (symmetric mixtures). The ordering of the fluid was much less intense for fluids of long chains (asymmetric mixtures), and some cases even show gas enrichment at the solid–liquid interface. Enrichment at the vapor–liquid interfaces and density inversion can also be observed. However, these effects are not as marked as in planar interfaces. The contact angle between the droplet and the substrate is calculated by fitting an ellipse to the vapor–liquid interface defined by the Gibbs dividing surface. In general, an increment in the concentration of the heavy component and a reduction of the temperature resulted in an increase of the contact angle, which in turn disfavored the wetting of the droplet.

中文翻译：

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Lennard-Jones 链二元混合物固着液滴的结构和接触角：分子动力学研究

进行分子动力学模拟以研究由与固体基质接触的 Lennard-Jones (LJ) 流体的二元混合物组成的圆柱形液滴。液滴由单体 LJ 流体加上每条链 2、10、20 和 30 个链段的线性切链的混合物组成，这些链通过谐波势和球形截断和移位的 Lennard-Jones 势相互作用。固体表面被建模为具有 FCC 结构的半无限铂基底，该结构通过 LJ 9-3 电位与流体相互作用。我们强调将单体 LJ 流体与重组分混合对接触角和液滴结构的影响，尤其是在液固区。液滴的密度分布揭示了在固液界面附近流体的强烈离散分层。分层在低温和短链混合物（对称混合物）下更为明显。对于长链流体（不对称混合物），流体的有序性要低得多，在某些情况下甚至在固液界面显示气体富集。还可以观察到汽液界面处的富集和密度反转。然而，这些效应不像平面界面那样明显。液滴和基材之间的接触角通过将椭圆拟合到由 Gibbs 分界面定义的汽液界面来计算。一般来说，