Scalable GW software for quasiparticle properties using OpenAtom

The GW method, which can describe electronic excitations accurately, is a powerful ab initio electronic structure technique in molecular, condensed matter and materials physics. However, the applications of the GW method to large systems requires supercomputers and efficient fine-grained parallel software to overcome the computational complexity and expense of the method which scales as O(N^4). Here, we develop fine-grained parallel GW software for the plane-wave basis. We proceed by revisiting the standard GW formulae in order to discern the optimal approaches for each phase of the GW calculation on present supercomputers and take into account recent methodological advances to inform our choices. These best numerical practices are implemented into the OpenAtom software which is written on top of Charm ++ parallel framework. We then evaluate the performance of our new software on a wide range of system sizes. Our GW software shows significantly improved parallel scaling compared to publicly available GW software on the Mira and Blue Waters supercomputers, two of most powerful computing platforms in the world.