界面吸附团簇演化与润湿机理研究

Study on the Mechanisms of Adsorption Cluster Evolution and Wetting at Solid-Vapor Interface

为了阐明界面吸附团簇的形成及其演化机理,采用理论分析和分子动力学模拟相结合的方法研究了氩在金表面的吸附特性,分析了吸附团簇演化过程与界面润湿机制。结果表明:吸附质以团簇形式吸附在固体表面吸附单元上,随着吸附的进行,表面零吸附单元减小并逐渐趋于零,单分子团簇不断生成;随着压比的增大,单分子团簇增长速率不断下降,当单分子团簇占比达到极大值之后,小分子团簇逐渐合并为大分子团簇。模拟得到的吸附单元数及团簇演化规律均与理论预测结果吻合很好。大压比下,团簇所含分子数增加,吸附层内原子平均能量降低,结构更稳定。探讨了吸附熵及界面张力的演化规律,当吸附熵达到极值时,发生吸附相变,并进一步确定了界面润湿条件。

In order to elucidate the formation and evolution mechanism of interfacial adsorption clusters,theoretical analysis and molecular dynamics simulations are hybrid to study the adsorption characteristics of argon on gold surface.The evolution process of adsorption cluster and interface wetting mechanism is clarified.Results showed that the adsorbate is adsorbed on the solid surface in the form of clusters.The empty adsorption sites decrease rapidly and asymptotically tend to zero,while the adsorbed single-molecular-clusters constantly form and occupy the surface adsorption sites as the adsorption proceeds.With the increase of pressure ratio,the growth rate of singlemolecular-clusters decreases.When the proportion of single-molecule-cluster reaches the maximum,the small sized clusters gradually merge and incubate into large sized clusters.Furthermore,the number of adsorption sites and the evolution of adsorption clusters obtained by molecular dynamics simulations are consistent with the theoretical calculations.For a relatively high pressure ratio,the number of molecules in the cluster increases,the average energy per atom in the adsorbate decreases,therefore,the structure of the adsorbate is more stable.Besides,the evolution of adsorption entropy and interfacial tension is discussed.For a certain pressure ratio,the adsorption entropy reaches the maximum value,and the adsorption phase transition occurs at the interface,and the wetting condition of the interface is determined.