Simulation of Thermal Stability and Friction: A Lubricant Confined Between Monolayers of Wear Inhibitors on Iron Oxide
Abstract
To understand antiwear phenomena in motor engines at the atomic level and provide evidence in selecting future ashless wear inhibitors, we studied the thermal stability of the self-assembled monolayer (SAM) model for dithiophosphate (DTP) and dithiocarbamate (DTC) molecules on the iron oxide surface using molecular dynamics. The interactions for DTP, DTC and Fe2O3 are evaluated based on a force field derived from fitting to ab initio quantum chemical calculations of dimethyl DTP (and DTC) and Fe(OH)2(H20)2-DTP (DTC) clusters. MD simulations at constant-NPT are conducted to asses relative thermal stabilities of the DTP and DTC with different pendant groups (n-propyl, i-propyl, n-pentyl, and i-pentyl). To investigate frictional process, we employ a steady state MD method in which one of the Fe2O3 slabs maintained at a constant linear velocity. We obtain the time averages normal and frictional forces from the interatomic forces. Then, we calculated the friction coefficient at the interface between SAMs of DTP and the confined lubricant, hexadecane, to asses the shear stability of DTPs with different pendant groups.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2003
- Accession Number
- ADA418136
Entities
People
- Alan L. Ho
- E. S. Yamaguchi
- R. Frazier
- Tahir Çağin
- Yifan Zhou
Organizations
- California Institute of Technology