Modeling nanoscale devices quantum mechanically is a computationally challenging problem where new methods to solve the underlying equations are in a dire need. In this paper, we present an approach to calculate the charge density in nanoscale devices, within the context of the non equilibrium Greens function approach. Our approach exploits recent advances in using an established graph partitioning approach. The developed method has the capability to handle open boundary conditions that are represented by full self energy matrices required for realistic modeling of nanoscale devices. Our method to calculate the electron density has a reduced complexity compared to the established recursive Greens function approach. As an example, we apply our algorithm to a quantum well superlattice and a carbon nanotube, which are represented by a continuum and tight binding Hamiltonian respectively, and demonstrate significant speed up over the recursive method.
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