Multiscale software for quantum simulations of nanostructured materials and devices

The development of robust, adaptive software and algorithms that can fully exploit exascale

capabilities and future computing architectures is critical to designing advanced materials and

devices with targeted properties. We have developed an open-source code that discretizes the

DFT equations on real-space grids that are distributed over the nodes of a massively parallel

system via domain decomposition. Multigrid techniques are used to dramatically accelerate

convergence while only requiring nearest neighbor communications. The real-space multigrid

(RMG) code achieves full plane wave accuracy and scales from desktops and clusters to

supercomputers consisting of ~200k cores and 20k GPUs, including the Cray XE-XK systems

and the new IBM-NVIDIA pre-exascale Summit. Multilevel parallelization with MPI, threads

and/or Cuda/HIP programming enables adaptation to future exascale supercomputers. RMG is

distributed via www.rmgdft.org, with over 3,800 downloads do date. Advanced functionalities

are provided through interfaces to other codes, including QMCPACK, BerkeleyGW, Phonopy,

and ALAMODE.