Atomistic Modeling of Chemomechanics at Electrified Interfaces

As the world moves to a more electrified future, addressing several mechanical and tribological challenges in electric systems ranging from electrical energy storage to electric vehicle powertrains requires a more fundamental understanding of chemomechanics of electrified interfaces. More detailed insights into the reactivity of surfaces under mechanical contact are needed to design novel materials/lubricants that are needed to improve the efficiency of electro-mechanical systems. In this study, we performed ab initio density functional theory (DFT) calculations and reactive molecular dynamics (RMD) simulations to understand the surface reactivity and evolution of tribolayers in surfaces under electrified and non-electrified contact. Atomistic simulations of Polyalphaolefin (PAO) lubricants on naturally-oxidized steel surfaces reveal the formation of amorphous non-stoichiometric iron-carbide tribolayers that are non-protective and contribute to surface wear, consistent with experimental observations. Reactive MD simulations, performed using a specially parameterized ReaxFF forcefield, were used to predict surface passivity and tribological performance at extreme conditions of temperature, pressure and electrification encountered near asperities in surfaces under mechanical loading and thus derive new design rules for surface structures and lubricants for electrified applications.