Quantitative Understanding of Atomic Wear Using Accelerated Molecular Simulation

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The goal of this proposed research is to develop a molecular-level understanding and a quantitative description of atomic wear during single-asperity sliding. Moving surfaces in contact can produce wear that shortens device lifetime and lowers energy efficiency. Molecular level simulations will be employed to understand how an amorphous silica tip blunts on a moving counter-surface under low loads. This simulation setup resembles the scanning of a silicon tip on polymer surfaces for high-density thermo-mechanical data storage, during which the native oxide layer of the silicon tip wears off. A novel accelerated molecular dynamics algorithm will be utilized to accelerate rare debris-generating events during sliding thus approach the experimental time scales. By simulating tip-sliding at various speeds, loads, contact areas and temperatures, the quantitative relation between the wear rate and loading conditions will be obtained. The applicability of the Archard's linear wear law and the nonlinear bond rupture model in the atomic wear regime will be critically evaluated.This research will enrich the fundamental knowledge on wear at the nanoscale, which is crucial for devising guidelines of operation conditions and estimating components lifetime for nanodevices with moving contacts, such as scanning probe-based memory storage, nanolithography as well as nano electromechanical systems. The computational platform developed here can also be used to investigate multi-asperity wear and tribochemical effects in the future. The educational components include outreach activities for high school students interested in science and engineering through the New Visions: Math, Engineering, Technology & Science (METS) program; curriculum development of a Modeling of Materials course at RPI; a continual effort on improving an open-source visualization software SimRePlay (www.simreplay.org) for the scientific community.