Abstract
Fundamental molecular issues in lubrication chemistry were reviewed under categories of solution chemistry, contact chemistry and tribochemistry. By introducing the Density Functional Theory(DFT)-derived chemical reactivity parameters (chemical potential, electronegativity, hardness, softness and Fukui function) and related electronic structural principles (electronegativity equalization principle, hard-soft acid-base principle, and maximum hardness principle), their relevancy to lubrication chemistry was explored. It was suggested that DFT, theoretical, conceptual and computational, represents a useful enabling tool to understand lubrication chemistry issues prior to experimentation and the approach may form a key step in the rational design of lubrication chemistry via computational methods. It can also be optimistically anticipated that these considerations will gestate unique DFT-based strategies to understand sophisticated tribology themes, such as origin of friction, essence of wear, adhesion in MEMS/NEMS, chemical mechanical polishing in wafer manufacturing, stress corrosion, chemical control of friction and wear, and construction of designer tribochemical systems.
Highlights
Probing adhesion, friction, wear, and lubrication at the molecular level has accelerated progress in the science of tribology
Owing to the atomic or molecular nature involved in these subjects, both physicists and chemists have begun exploring quantum mechanics (QM) and quantum chemistry (QC) to understand the fundamental physics and chemistry in the practical tribosystems or tribochemical systems
1) Lubrication chemistry is generally explored from solution chemistry, contact chemistry and tribochemistry
Summary
Friction, wear, and lubrication at the molecular level has accelerated progress in the science of tribology. In application of QC algorithms to lubrication chemistry, Dr Yamaguchi of Chevron has led a group devoting to develop antiwear models of zinc dithiophosphates based on their local charges calculated by ab initio QC [13,14] In her widely lectured subject, Quantum Mechanics and the Automobile, Dr Chaka of Lubrizol has demonstrated that nowadays DFT is already used by the chemical industry to illuminate chemical processes underlying the performances of lubricants and additives [15]. DFT-derived concepts, which presents inherent coherence of chemical hardness, LUMO-HOMO gap between the anti-bonding and bonding molecular orbitals of molecules, as called by chemists, and the band gap between the conduction and valence energy bands of solids (Eg), as dubbed by physicists
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