Mathas Dimitrios, Sarpa Davide, Holweger Walter, Wolf Marcus, Bohnert Christof, Bakolas Vasilios, Procelewska Joanna, Franke Joerg, Rödel Philipp, Skylaris Chris-Kriton
Department of Chemistry, University of Southampton Highfield Southampton SO17 1BJ UK
Mechanical Engineering Department, University of Southampton Highfield Southampton SO17 1BJ UK.
RSC Adv. 2023 Nov 21;13(48):33994-34002. doi: 10.1039/d3ra06929j. eCollection 2023 Nov 16.
The behaviour of confined lubricants at the atomic scale as affected by the interactions at the surface-lubricant interface is relevant in a range of technological applications in areas such as the automotive industry. In this paper, by performing fully atomistic molecular dynamics, we investigate the regime where the viscosity starts to deviate from the bulk behaviour, a topic of great practical and scientific relevance. The simulations consist of setting up a shear flow by confining the lubricant between iron oxide surfaces. By using confined Non-Equilibrium Molecular Dynamics (NEMD) simulations at a pressure range of 0.1-1.0 GPa at 100 °C, we demonstrate that the film thickness of the fluid affects the behaviour of viscosity. We find that by increasing the number of lubricant molecules, we approach the viscosity value of the bulk fluid derived from previously published NEMD simulations for the same system. These changes in viscosity occurred at film thicknesses ranging from 10.12 to 55.93 Å. The viscosity deviations at different pressures between the system with the greatest number of lubricant molecules and the bulk simulations varied from -16% to 41%. The choice of the utilized force field for treating the atomic interactions was also investigated.
在诸如汽车工业等领域的一系列技术应用中，受表面 - 润滑剂界面相互作用影响的受限润滑剂在原子尺度上的行为具有重要意义。在本文中，通过进行全原子分子动力学模拟，我们研究了粘度开始偏离本体行为的区域，这是一个具有重大实际和科学意义的课题。模拟包括通过将润滑剂限制在氧化铁表面之间来建立剪切流。通过在100°C、0.1 - 1.0 GPa的压力范围内使用受限非平衡分子动力学（NEMD）模拟，我们证明了流体的膜厚会影响粘度行为。我们发现，通过增加润滑剂分子的数量，我们接近了先前针对同一系统发表的NEMD模拟得出的本体流体的粘度值。这些粘度变化发生在膜厚范围为10.12至55.93 Å之间。具有最多润滑剂分子的系统与本体模拟在不同压力下的粘度偏差在 - 16%至41%之间变化。我们还研究了用于处理原子相互作用的所采用力场的选择。
