Enhancement of the GW Space-Time Program Code for Accurate Prediction of the Electronic Properties of Organic Electronics Materials

For large-scale efficiently parallelized electronic structure calculation within the GW approximation, we modified the MPI-parallelized version of the GW space-time program. To reduce the communication time required for computation of the inverse of the complex dielectric matrix, which is one of the bottlenecks of the program, the ScaLapack library codes employed for the LU-decomposition matrix inversion was replaced with the Lapack counterpart implemented with the intranode task parallelization. As a result, the elapsed time for matrix inversion significantly reduced, along with improvement on the parallelization efficiency for the number of nodes or cores. In addition, the intranode task parallelization for inversion with OpenMP was found to show reasonable parallelization efficiency with respect to the number of threads inside a node. Overall, the improvement in computation time will allow us to investigate not only the electronic structure of bulk phases, but also those of surfaces and interfaces of organic molecular crystals.