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Structures, Vibrations, and Force Fields of Dithiophosphate Wear Inhibitors from ab Initio Quantum Chemistry

Jiang, Shaoyi and Dasgupta, Siddharth and Blanco, Mario and Frazier, Rawls and Yamaguchi, Elaine S. and Tang, Yongchun and Goddard, William A., III (1996) Structures, Vibrations, and Force Fields of Dithiophosphate Wear Inhibitors from ab Initio Quantum Chemistry. Journal of Physical Chemistry, 100 (39). pp. 15760-15769. ISSN 0022-3654. doi:10.1021/jp960649j.

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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.

Item Type:Article
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URLURL TypeDescription Information
Dasgupta, Siddharth0000-0002-9161-7457
Goddard, William A., III0000-0003-0097-5716
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.
Funding AgencyGrant Number
Chevron Chemical Co.UNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
NSFASC 92-100368
Chevron Petroleum Technology Co.UNSPECIFIED
Hughes Research LaboratoriesUNSPECIFIED
Chevron Research and Technology Co.UNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
Issue or Number:39
Record Number:CaltechAUTHORS:20180720-142734765
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Official Citation:Structures, Vibrations, and Force Fields of Dithiophosphate Wear Inhibitors from ab Initio Quantum Chemistry Shaoyi Jiang, Siddharth Dasgupta, Mario Blanco, Rawls Frazier, Elaine S. Yamaguchi, Yongchun Tang, and William A. Goddard, III The Journal of Physical Chemistry 1996 100 (39), 15760-15769 DOI: 10.1021/jp960649j
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:88083
Deposited By: George Porter
Deposited On:23 Jul 2018 20:20
Last Modified:16 Nov 2021 00:23

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