Ab Initio Transport Calculations for Functionalized Graphene Flakes on a Supercomputer

Abstract

We present ab initio transport studies of large graphene flakes focusing on the local current density j(r) as it arises from a dc-transport measurement. Such ab initio transport calculations for sufficiently large flakes can be successfully tackled only using well scaling ab initio packages capable for transport calculations in thin film geometries. We employ the FHI-aims /AitransS packages to study the effect of disorder on the local current density in graphene flakes, in particular, the effect of chemical functionalization on mesoscopic fluctuations of the current density. Simulating graphene flakes with several thousands of atoms, we clearly see the qualitative effects of quantum interference and mesoscopic fluctuations in such systems. We also discuss the parallelization and optimization techniques, which we implemented into the transport module AitransS to allow efficient ab initio transport calculation on Cray XE6 and XC40 supercomputers.