有机二硫化物极压添加剂结构与润滑性能的理论研究

运用Gaussian98量子化学程序包,采用密度泛函理论(DFT)及从头算(ab initio)方法,在B3LYP/6-31G和HF/6-31G水平上对12种有机二硫化物的分子几何构型、电子结构、分子轨道指数及与铁原子簇的相互作用等进行了理论计算;由前线分子轨道理论分析了反应的活性原子和活性键,运用轨道能量近似原则讨论了有机二硫化物与铁原子的作用方式;以前线电子密度、超离域性指数和原子净电荷等参数作为表征有机二硫化物与金属作用强弱的判据,分析了有机二硫化物与铁原子间键合的强弱及反应性大小.结果表明:当有机二硫化物与铁接触时,趋向于发生S-S键和C-S键断裂;随碳链的增长,有机二硫化物的抗磨性能增强,极压性能减弱,与相应的摩擦磨损试验结果一致.所用的量子化学方法在润滑添加剂结构-性能研究领域具有良好的应用前景,可用以指导润滑添加剂的分子设计.

Theoretical Study on the Structure and Lubricating Properties of Disulfide Compounds as Extreme Pressure Additive

The molecular geometries optimization and electronic structures for twelve disulfide compounds were investigated making use of density functional theory (DFT) and ab initio method at the 6-31G basis set level. The active atoms and reaction bonds of the disulfides with respect to iron atom cluster were determined making use of frontier molecular orbital theory. The interaction pattern between the organic disulfide compounds and iron atom cluster was discussed based on the approximate rule of orbital energy. Some parameters characterizing the action strength between the organic disulfide compounds and iron atom cluster, including the bonding strength, reactive strength, and static action strength, were analyzed using frontier electron density, super de-localizability, and net atomic charge as criteria. The results indicated that the S-S and C-S bonds of the compounds would be preferentially broken in interacting with the metal surface. The anti-wear ability of the disulfide compounds as the additives was strengthened and the extreme pressure performance weakened with increasing carbon chain. The prediction results based on quantum chemistry calculations were in good accordance with the relevant friction and wear test results, which might provide reliable reference data for the molecular design of novel high-performance antiwear and extreme pressure additives.