Accelerated Molecular Dynamics Simulations of Atomic Force Microscope Experiments.

Molecular Dynamics Simulation;Hyperdynamics;Mechanical Engineering;Engineering;Mechanical Engineering

Kim, Woo KyunKurabayashi, Katsuo ;

University of Michigan

关键词: Molecular Dynamics Simulation;    Hyperdynamics;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/63767/wkkim_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

We apply an accelerated molecular dynamics (MD) methodology to simulate Atomic Force Microscope (AFM) experiments. New methods using hyperdynamics and a parallel algorithm make it possible to extend the simulation time scale and to model an AFM tip with a sliding velocity close to the actual experimental values. MD simulations of AFM models with simple geometry validate these methodologies. We model AFM experiments by which researchers observed ultralow friction forces between incommensurate surfaces, a phenomenon called superlubricity. The simulation results reveal that superlubricity breaks down with softer tips and at higher normal loads, and that several metastable states exist during the stick phase with softer tips. Additional simulations with a silicon tip and a silicon surface with oxidized layers model recent AFM experiments regarding variations in the relationship between friction force and sliding velocity with respect to changes in temperature. The simulations utilize a modified Stillinger-Weber potential, which can treat both pure silicon and silica simultaneously, and the bond-boost method for hyperdynamics simulation. We compare the simulation results with the experimental data to elucidate the atomic level processes that occur during sliding. The simulation results indicate that the deviation from the Tomlinson model predictions at higher temperatures and lower sliding velocities may arise from the bond breaking and formation mechanism at the interface.