Title: Seamless elastic boundaries for lattices in molecular dynamics simulation
Presenter: Tristan Sharp
Affiliation: Johns Hopkins University
Abstract: Molecular dynamics (MD) simulation is often used to model phenomena at solid interfaces, but capturing long-range deformations within the solid can require very large system sizes. Multiscale methods can reduce the computational expense by, for example, connecting an MD region at the surface to a coarser finite-element method within the bulk. However, in general, these methods either produce a model with no underlying Hamiltonian or suffer from ghost forces near the interface. Both problems can be avoided by instead using a Green's function technique most recently proposed by Campañá and Müser for solid lattices 1. Typically, at some depth within the solid, beyond some atomic lattice plane, strain gradients are small and the linear mechanical response easily suffices. The Hamiltonian of the underlying atomic layers can be replaced with its harmonic approximation and integrated out at the beginning of the simulation. The Green's function MD (GFMD) package illustrates the capability to eliminate huge portions of the simulation geometry and dramatically reduce computation time, while retaining accurate deformations 2. The method has been formulated in a general way for both pair-potential and many-body interactions and several lattice types.
1 C. Campañá and M. Müser, Phys. Rev. B 74, 075420 (2006).
2 L. Pastewka, T. Sharp, and M. O. Robbins, Phys. Rev. B 86, 075459 (2012).