Structures, Vibrations, and Force Fields of Dithiophosphate Wear Inhibitors from ab Initio Quantum Chemistry
Abstract
Zinc dithiophosphates (ZnDTPs) are ubiquitous lubricating oil additives in today's passenger car motor oils, providing the important functions of wear and oxidation inhibition. However, the molecular-level mechanism by which these materials reduce wear is not understood. As a first step in developing an understanding of this mechanism, we used ab initio quantum chemical methods to examine the structures, vibrations, and energetics of these systems. The results show that the two phosphorus−sulfur bonds of the dithiophosphate of ZnDTPs are equivalent and have character intermediate between single and double bonds. This contrasts with the paradigm of one double bond (P=S) and one single bond (P−S) often used. Vibrational studies of DTP systems lead to a strong IR transition at about 650 cm^(-1) and a weak transition at about 530 cm^(-1). We find modes in good agreement with experiment, where the high-frequency mode is antisymmetric P=S stretch (not PS), while the lower mode is symmetric PS stretch (not P−S). On the basis of the ab initio calculation results, we used the biased Hessian method to develop a vibrationally accurate force field (FF) for ZnDTPs. This FF can be used to examine the binding of DTPs to metal and metal oxide surfaces.
Additional Information
© 1996 American Chemical Society. Received: February 29, 1996; In Final Form: June 28, 1996. This research was supported by the Chevron Chemical Co. (Oronite Technology Group), by the DOE-BCTR, and by NSF GCAG (ASC 92-100368). The facilities of the MSC are also supported by grants from Chevron Petroleum Technology Co., Asahi Chemical, Aramco, Asahi Glass, BP Chemical, Hercules, Xerox, Hughes Research Lab., Chevron Research and Technology Co., and Beckman Institute. Part of the calculations were carried out at the San Diego Supercomputer Center, the Pittsburgh Supercomputer Center, and National Center for Supercomputer Applications, and the JPL Supercomputer Center.Attached Files
Supplemental Material - jp15760.pdf
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Additional details
- Eprint ID
- 88083
- DOI
- 10.1021/jp960649j
- Resolver ID
- CaltechAUTHORS:20180720-142734765
- Chevron Chemical Co.
- Department of Energy (DOE)
- ASC 92-100368
- NSF
- Chevron Petroleum Technology Co.
- Asahi Chemical
- Aramco
- Asahi Glass
- BP Chemical
- Hercules
- Xerox
- Hughes Research Laboratories
- Chevron Research and Technology Co.
- Caltech Beckman Institute
- Created
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2018-07-23Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field