Development of Tribochemical Reaction Simulator Based on Hybrid Quantum Chemical Molecular Dynamics Method

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Recently, the demands on the clarification of tribochemical reactions that are tribological phenomena including chemical reactions have increased in electronic level. The objectives of this study are to pioneer the development of a novel tribochemical simulator for clarification of tribochemical reactions by integrating our developed simulators, Colors, accelerated quantum chemical molecular dynamics program, and TRIBOSIM, tribology simulator based on molecular dynamics techniques for clarification of tribological phenomena in atomistic level, and to design theoretically tribological materials and processes in electronic level. From FY 2004 to FY 2005, we succeeded to develop a novel tribochemical simulator based on Colors and TRIBOSIM, hybrid quantum chemical molecular dynamics program, Hybrid-Colors as well a novel tribochemical simulator based on Hybrid-Colors code. On FY 2006, chemical reaction dynamics of molybdenum dialkyldithiocarbamate (MoDTC), which has been used as a friction modifier in automotive engine oils, on iron oxide surfaces was investigated. It was found that the alkyl groups of MoDTC were dissociated. Finally, Mo-S bonds formed by chemical reaction of MoDTC were left on the iron oxide surfaces. Regarding tribochemical reaction dynamics of trimethylphosphate (TMP) as the extreme pressure additives for automotive engine oils, was studied. As a result, it was clarified that Fe and O atoms of TMP formed new bonds only under friction condition. On FY 2007, it was revealed that a large contribution of Coulombic repulsion between S atoms located at the different atomic layers in MoS_2 decrease the friction ascribed in the sliding phenomena of boundary layers of MoS_2, which is formed at the rubbing interface by MoDTC under boundary lubrication condition. As a conclusion, it was demonstrated that our novel tribochemical simulators developed in this study were effective on the clarification of tribochemical reactions and tribological properties.