Large-scale density-functional calculations in real space and its application to bilayer graphene and semiconductor epitaxial growth

Facing current and future massively parallel architecture of supercomputers, we need to make close collaboration between the fields of physical science and computer science. Such collaboration we name COMPUTICS is already in progress (http://computics-material.jp/index-e.html). I here explain an example of such collaboration which allows us to perform total-energy electronic-structure calculations based on the density-functional theory (DFT) in the real-space scheme for tens-of-thousands-atom systems and also the real-space Car-Parrinello Molecular Dynamics simulations for thousands-of-atom systems. I first explain how we are able to perform such large-scale computations efficiently in our code named RSDFT. Recent development of the device simulation combined with the non-equilibrium Green’s function (NEGF) method and its application to Si nanowire MOSFETs are also reported. As examples of the application to materials science, I will discuss (1) the localization of Dirac electrons induced by moire pattern in twisted bilayer graphene, (2) ammonia decomposition and N incorporation on epitaxially grown GaN films, (3) intrinsic carrier traps near SiC/SiO2 interfaces, and possibly (4) the formation of amorphous systems with thousands of atoms.
In collaboration with J.-I Iwata (Advance Soft), D. Takahashi (U Tsukuba), G. Milnikov (Osaka U), N. Mori (Osaka U), K. Uchida (Kyoto Inst Tech), Y.-i. Matsushita (Tokyo Inst Tech), K. M. Bui (Nagoya U), M. Boero (Strasbourg U), and K. Shiraishi (Nagoya U).