Parallel empirical pseudopotential electronic structure calculations for million atom systems

We present a parallel implementation of the previously developed folded spectrum method for empirical pseudopotential electronic structure calculations. With the parallel implementation we can calculate a small number of electronic states for systems of up to one million atoms. A plane-wave basis is used to expand the wavefunctions in the same way as is commonly used in ab initio calculations, but the potential is a fixed external potential generated using atomistic empirical pseudopotentials. Two techniques allow the calculation to scale to million atom systems. First, the previously developed folded spectrum method allows us to calculate directly a few electronic states of interest around the gap. This makes the scaling of the calculation O (N) for an N atom system and a fixed number of electronic states. Second, we have now developed an efficient parallel implementation of the algorithm that scales up to hundreds of processors, giving us the memory and computer power to simulate one million atoms. The program's performance is demonstrated for many large semiconductor nanostructure systems. (C) 2000 Academic Press.