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Diffusive Molecular Dynamics

Diffusive Molecular Dynamics. Ju Li, Bill Cox, Tom Lenosky, Ning Ma, Yunzhi Wang Ohio State University. Traditional MD numerically integrates Newton’s equation of motion over 3 N degrees of freedom, the atomic positions:.

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Diffusive Molecular Dynamics

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  1. Diffusive Molecular Dynamics Ju Li, Bill Cox, Tom Lenosky, Ning Ma, Yunzhi Wang Ohio State University

  2. Traditional MD numerically integrates Newton’s equation of motion over 3N degrees of freedom, the atomic positions: It is difficult to reach diffusive time scales using traditional MD due to timestep (~ ps / 100), which needs to resolve atomic vibrations. Traditional Molecular Dynamics

  3. Diffusive MD: The Idea Variational Gaussian Method Lesar, Najafabadi and Srolovitz, Phys. Rev. Lett. 63 (1989) 624. DMD ci: occupation probability (vacancy, solutes) Define mi for each atom, to drive diffusion Ferris wheel seen with long camera exposure time

  4. Variational Gaussian Method VG free energy true free energy {xi,ai}

  5. Comparison with Monte Carlo Lesar, Najafabadi and Srolovitz, Phys. Rev. Lett. 63 (1989) 624.

  6. DMD thermodynamics DMD view VG view

  7. DMD kinetics nearest-neighbor network

  8. DMD is atomistic realization of regular solution model, with gradient thermo, long-range elastic interaction, and short-range coordination interactions all included. • DMD kinetics is “solving Cahn-Hilliard equation on a moving atom grid”, with atomic spatial resolution, but at diffusive timescales. • The “quasi-continuum” version of DMD can be coupled to well-established diffusion-microelasticity equation solvers such as phase-field method. • No need to pre-build event catalog. Could be competitive against kinetic Monte Carlo.

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