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11:00-11:30Invited: Atsushi OshiyamaLarge-Scale Real-Space Density-Functional Calculations: Moire-Induced Electron Localization in Graphene & Floating Electron States in SiC
Current architecture of supercomputers consists of a huge number of massively paralleled compute nodes. This situation demands us to make close and exciting collaboration among the fields of physical science, applied mathematics and computer science. Such collaboration we name COMPUTICS has been already started (http://computics-material.jp/index-e.html). I explain an example of such collaboration which allows us to perform electronic-structure calculations based on the density-functional theory (DFT) for tens-of-thousands atom systems. The scheme we have adopted is the real-space (RS) scheme in the density functional theory (DFT) combined with the pseudo-potential technique. Our code RSDFT highly optimized to the current architecture of the supercomputer was awarded ACM Gordon-Bell prize in peak performance in 2011.
After explaining the essence of RSDFT, I report on the two issues in semiconductor physics. First, our large-scale DFT calculations for twisted bilayer graphene (tBLG) reveal the existence of the critical twist angle above which the two graphene layers are essentially decoupled and below which the Dirac electrons are localized due to Moire pattern. Second, in SiC, our calculations clarify that the electron states of the conduction bands of covalent semiconductors are distributed mainly in the interstitial channels and that this floating nature leads to the experimentally observed band-gap variation and the anisotropic effective masses in various polytypes of SiC.11:30-11:45Open11:45-12:00Oral: Marco BernardiThe First Picosecond after Sunlight Absorption in Si & GaAs from First-Principles Calculations
Co-authors: Derek Vigil-Fowler, Jeffrey B. Neaton, Steven G. Louie12:00-12:15Oral: Piotr BoguslawskiGallium Vacancy & Mn & Fe Ions in GaN by GGA+U Calculations: How Big is +U Term?
Co-authors: Tomasz Zakrzewski, Oksana Volnianska12:15-12:30Oral: Wei ChenBand Offsets of Lattice-Matched Semiconductor Heterojunctions through Hybrid Functionals & GW
Co-authors: Karim Steiner, Alfredo Pasquarello 12:30-12:45Open12:45-13:00Open