体液相之间受限的气体纳米薄膜的分子层面研究
Molecular Insights into Gas Nanofilms Confined Between Bulk Liquid Phases
AI总结：
本研究通过分子动力学模拟，以 Lennard-Jones 氩气为模型，揭示了体液相间受限气体纳米薄膜的形态转变规律、热力学性质及与经典密度泛函理论的偏差机制，为相关多相过程提供了分子层面见解。
AI中文摘要：
纳米级厚度的流体薄膜在受限多相过程中发挥着关键作用，但与液体纳米薄膜相比，自由气体纳米薄膜的热力学性质和稳定性仍鲜为人知。本研究采用分子动力学（MD）模拟，以 Lennard-Jones 氩气为模型体系，系统探究体液相之间受限的气体纳米薄膜。结果表明，表面张力随薄膜厚度减小呈指数下降，同时负分离压力的幅值增大；薄膜变薄时，平面气体薄膜会通过液桥的形成与生长，发生从稳定平面态到瞬态或持续球形气泡的明显形态转变。薄膜表面积对其热力学性质影响显著，表面积越大，厚度依赖性越强，与经典密度泛函理论（cDFT）预测的偏差也越大；较小表面积下 MD 与 cDFT 的吻合度更高，说明偏差主要源于热毛细波涨落——该涨落包含在 MD 中，却被平均场 cDFT 忽略。此外，在薄膜厚度较小时，分离压力的幅值随温度降低而增大，这与受限气相对厚度变化的敏感性增强一致，且与液体纳米薄膜的一般报道趋势相反。这些发现为气体纳米薄膜的热力学性质和稳定性提供了分子层面的见解，对受限多相传输和液滴聚并具有重要意义。
英文摘要：
Nanometer-thick fluid films play a critical role in confined multiphase processes, yet the thermodynamics and stability of free gas nanofilms remain poorly understood compared with their liquid counterparts. Here, molecular dynamics (MD) simulations are employed to systematically investigate gas nanofilms confined between bulk liquid phases using Lennard-Jones argon as a model system. The results show that the surface tension decreases exponentially with decreasing film thickness, accompanied by an increasing magnitude of the negative disjoining pressure. Upon thinning, the planar gas film undergoes a distinct morphological transition from a stable planar state to a transient or persistent spherical bubble through the formation and growth of a liquid bridge. The film surface area strongly affects its thermodynamic properties, with larger areas producing stronger thickness dependence and larger deviations from classical density functional theory (cDFT) predictions. The closer agreement between MD and cDFT at smaller surface areas suggests that the discrepancy primarily arises from thermal capillary-wave fluctuations, which are included in MD but omitted in mean-field cDFT. Moreover, at small film thicknesses, the magnitude of the disjoining pressure increases with decreasing temperature, consistent with the enhanced sensitivity of the confined gas phase to thickness variations and contrasting with the trend generally reported for liquid nanofilms. These findings provide molecular insights into the thermodynamics and stability of gas nanofilms, with implications for confined multiphase transport and droplet coalescence.
