二烷基二硫代磷酸锌(ZDDP)的成键特征与润滑机理的理论研究

Theoretical Study on the Structure and Lubrication Mechanism of Zinc Dialkydithiophosphate (ZDDP)

采用量子化学从头算法,全优化计算了二烷基二硫代磷酸锌(ZDDP)化合物的平衡几何构型和成键特征,用前线轨道能级和组成以及前线电子密度等参数,探讨了ZDDP的润滑机理.研究表明ZDDP的活性元素为2种位置上的S元素,ZDDP与铁摩擦副作用最可能的断键位置是S-P和P=S键.随后S-P和P=S键的断裂,S及分解产物继续与铁摩擦副表面反应,形成由多磷酸盐和铁的硫化物组成的反应膜,从而有效地降低摩擦磨损.计算结果与摩擦学实验结果一致.

The geomtetric structure, frontier orbital coefficients and frontier electron densities of the important lubricating oil additive Zinc dialkydilhiophosphale （ZDDP） are investigated by nsing ab initio method. The results show thai the HOMO of ZDDP is mainly ctmposed by p atomic orbilal of sulphur atoms and the frontier electron densities （focc ） of them are higher than the other elements of ZDDP, thus it can be deduced that the sulphus atoms are the most likely flints of attack during the surface reaction. The attack causes the cleavage of S- P and P=S bonds, then the decomposition produets reacting with the surface of Fe metal lead to the formation of the anti - wear and anti - friclion film largely composed of polyphosphates and sulphides. The prediction mechanism of the film formnation is in good general agreement with experimental observations.