Large-Scale Electronic Structure Calculations with Real-Space grid Density-Functional Theory code

First-principles quantum-mechanical electronic structure calculations based on the density-functional theory (DFT) is an important ingredient of material sciences. The system sizes handled in usual DFT calculations are limited within a thousand of atoms due to the computational complexity of fully quantummechanical approaches. Real-space DFT (RSDFT) code, which has been developed in our group, is a promising application to overcome the size difficulty in first-principles quantum mechanical calculations. RSDFT is developed based on the real-space grid formulation of DFT [1] instead of conventional reciprocal-space formulation, in which frequent use of fast Fourier transform (FFT) is inevitable, so that it’s suitable for massively-parallel computers such as K computer [2]. Recently, we have performed electronic structure calculations for silicon nanowires with 10,000 to 1000,000 atoms by using RSDFT on the K computer with very high performance, and we got Gordon-Bell prize in 2011 with this work. In this paper, I review the first-principles electronic structure calculations in DFT and our program code RSDFT. In addition, I give an introduction on the technological importance of our target system silicon nanowire (SiNW), and discuss the results of the calculations for that system.