  In this work, we have developed a multiscale computational algorithm to
couple finite element method with an open source molecular dynamics code ---
the Large scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) --- to
perform hierarchical multiscale simulations in highly scalable parallel
computations. The algorithm was firstly verified by performing simulations of
single crystal copper deformation, and a good agreement with the
well-established method was confirmed. Then, we applied the multiscale method
to simulate mechanical responses of a polymeric material composed of
multi-million fine scale atoms inside the representative unit cells (r-cell)
against uniaxial loading. It was observed that the method can successfully
capture plastic deformation in the polymer at macroscale, and reproduces the
double yield points typical in polymeric materials, strain localization and
necking deformation after the second yield point. In addition, parallel
scalability of the multiscale algorithm was examined up to around 100 thousand
processors with 10 million particles, and an almost ideal strong scaling was
achieved thanks to LAMMPS parallel architecture.
