Molecular Foundry Seminar

"Bridging the Timescale Gap Between Simulations and Experiments
Using Accelerated Molecular Dynamics"

Dr. Danny Perez, Theoretical Division, Los Alamos National Laboratory
Tuesday, February 1st at 1:30 pm, Bldg. 67 - 3111

View the Foundry Seminar Schedule

Abstract:

Most materials possess an extremely wide range of characteristic timescales. Though vibrational motion occurs over picoseconds, microseconds can be required for local conformational changes. Nanostructures globally evolve on even longer timescales, typically milliseconds or more. Many important phenomena are therefore totally inaccessible to direct dynamical  simulations using molecular dynamics (MD), because MD is limited to timescales of microseconds or less. This rather severe limitation often makes correspondence between simulations and experiments very difficult.

The last decade has seen the development of Accelerated  Molecular Dynamics (AMD) methods that mitigate this problem by enabling simulations over very long timescales while retaining full atomistic accuracy. In this talk, I will use two examples, namely plasticity in strained nanowires and friction at nanoscale interfaces, to illustrate the ability of AMD to bridge the timescale gap and to provide crucial insights into the nanoscale behavior of materials. In the case of nanowires,  AMD simulations reaching up to a millisecond are used to identify the atomistic mechanisms that lead to plastic deformation and failure. In the case of friction, AMD is used to validate a rate theory that predicts tribological characteristics over a wide range of conditions. Finally, I will also discuss how, e.g. through coupling with multiscale techniques, AMD methods can be generalized to further extend their reach and improve their predictive power.