Ayestarán Latorre Carlos, Remias Joseph E, Moore Joshua D, Spikes Hugh A, Dini Daniele, Ewen James P
Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK.
Department of Materials, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK.
Commun Chem. 2021 Dec 16;4(1):178. doi: 10.1038/s42004-021-00615-x.
The molecular structure of lubricant additives controls not only their adsorption and dissociation behaviour at the nanoscale, but also their ability to reduce friction and wear at the macroscale. Here, we show using nonequilibrium molecular dynamics simulations with a reactive force field that tri(s-butyl)phosphate dissociates much faster than tri(n-butyl)phosphate when heated and compressed between sliding iron surfaces. For both molecules, dissociative chemisorption proceeds through cleavage of carbon-oxygen bonds. The dissociation rate increases exponentially with temperature and stress. When the rate-temperature-stress data are fitted with the Bell model, both molecules have similar activation energies and activation volumes and the higher reactivity of tri(s-butyl)phosphate is due to a larger pre-exponential factor. These observations are consistent with experiments using the antiwear additive zinc dialkyldithiophosphate. This study represents a crucial step towards the virtual screening of lubricant additives with different substituents to optimise tribological performance.
润滑剂添加剂的分子结构不仅控制其在纳米尺度上的吸附和解离行为，还控制其在宏观尺度上减少摩擦和磨损的能力。在此，我们使用具有反应力场的非平衡分子动力学模拟表明，当在滑动铁表面之间加热和压缩时，磷酸三（仲丁基）酯的解离速度比磷酸三（正丁基）酯快得多。对于这两种分子，解离化学吸附通过碳 - 氧键的断裂进行。解离速率随温度和应力呈指数增加。当速率 - 温度 - 应力数据用贝尔模型拟合时，两种分子具有相似的活化能和活化体积，并且磷酸三（仲丁基）酯的较高反应活性归因于较大的指前因子。这些观察结果与使用抗磨添加剂二烷基二硫代磷酸锌的实验一致。这项研究代表了朝着虚拟筛选具有不同取代基的润滑剂添加剂以优化摩擦学性能迈出的关键一步。
