Publications

Zimmerman, Jonathan A.; Song, Bo S.; Thompson, Aidan P.; Medlin, Douglas L.; San Marchi, Christopher W.

Abstract not provided.

Thompson, Aidan P.; Lane, James M.; Zimmerman, Jonathan A.

Molecular dynamics simulation (MD) is an invaluable tool for studying problems sensitive to atomscale physics such as structural transitions, discontinuous interfaces, non-equilibrium dynamics, and elastic-plastic deformation. In order to apply this method to modeling of ramp-compression experiments, several challenges must be overcome: accuracy of interatomic potentials, length- and time-scales, and extraction of continuum quantities. We have completed a 3 year LDRD project with the goal of developing molecular dynamics simulation capabilities for modeling the response of materials to ramp compression. The techniques we have developed fall in to three categories (i) molecular dynamics methods (ii) interatomic potentials (iii) calculation of continuum variables. Highlights include the development of an accurate interatomic potential describing shock-melting of Beryllium, a scaling technique for modeling slow ramp compression experiments using fast ramp MD simulations, and a technique for extracting plastic strain from MD simulations. All of these methods have been implemented in Sandia's LAMMPS MD code, ensuring their widespread availability to dynamic materials research at Sandia and elsewhere.

Deng, Jie D.; Erickson, Lindsay C.; Plimpton, Steven J.; Thompson, Aidan P.; Zhou, Xiaowang Z.; Zimmerman, Jonathan A.

Many of the most important and hardest-to-solve problems related to the synthesis, performance, and aging of materials involve diffusion through the material or along surfaces and interfaces. These diffusion processes are driven by motions at the atomic scale, but traditional atomistic simulation methods such as molecular dynamics are limited to very short timescales on the order of the atomic vibration period (less than a picosecond), while macroscale diffusion takes place over timescales many orders of magnitude larger. We have completed an LDRD project with the goal of developing and implementing new simulation tools to overcome this timescale problem. In particular, we have focused on two main classes of methods: accelerated molecular dynamics methods that seek to extend the timescale attainable in atomistic simulations, and so-called 'equation-free' methods that combine a fine scale atomistic description of a system with a slower, coarse scale description in order to project the system forward over long times.

Deng, Jie D.; Plimpton, Steven J.; Thompson, Aidan P.; Zimmerman, Jonathan A.

Abstract not provided.

Lane, James M.; Thompson, Aidan P.; Zimmerman, Jonathan A.

Abstract not provided.

Zimmerman, Jonathan A.; Collis, Samuel S.; Fang, H.E.; Lee, Jean L.; Lehoucq, Richard B.; Moody, Neville R.; Plimpton, Steven J.

Abstract not provided.