Computational Materials Science Seminars

Latest News

  • Ternary nanoclusters composed of rare metal atoms are expected as NOx reduction catalysts and are being actively studied experimentally. However, the details of the physical factors that govern the structure of nanoclusters have not been clarified. This time, we analyzed the structural properties of the ternary PdRuM (M = Pt, Rh, Ir) nanoclusters (about 55 atoms) in detail using first-principles calculation and Monte Carlo method. We figured out that in the case of naked clusters, Pd atoms with low surface energy are near the surface and tend to be located at the top of nanoclusters, and Ru atoms tend to aggregate in the core region of the cluster. Furthermore, it became clear that the interatomic distance near the surface tends to shrink more than in the case of a solid, and the degree of shrinkage is related to the number of occupied d-orbitals. On the other hand, it was found that when the surface is oxidized, Ru atoms move from the nuclear region to the vicinity of the surface and have a chemical bond with oxygen, which greatly stabilizes the cluster. These calculations suggest that the stable structure may change depending on the oxidation state of the nanoclusters.
    The research results were published in RSC Advances. This was conducted in collaboration with Yamamuro Research Group of ISSP, The University of Tokyo. [2020/4/27]
    For more details, please see here.

  • We have constructed a highly accurate interatomic potential of body-centered cubic lattice (BCC) iron by a machine learning technique based on the neural network (NN) method. In order to quantitatively understand the mechanical properties of BCC iron at the atomic level, an interatomic potential that can accurately reproduce the dislocation dynamics needs to be developed, while the embedded atom method (EAM) potential, which has been widely used so far, may not have enough accuracy. The NN potential we have constructed in this study can not only reproduce the Peierls barrier of the dislocation core by the first-principles calculation, but also accurately calculate the energy profile of the screw dislocation core. The newly developed NN potential is expected to apply for large-scale molecular dynamics simulations to investigate the mechanical properties of BCC iron.
    The research results were published in Phys. Rev. Materials. This was conducted in collaboration with Mori Research Group of College of Industrial Technology. [2020/4/24]
    For more details, please see here.

  • The density functional theory for superconductors is a method to obtain the superconducting transition temperature (Tc) from the first principles. It can take the electron-phonon interaction, the electron Coulomb interaction, and the spin fluctuation effect in a non-empirical way to do the calculation.We have formulated a method to handle the spin fluctuation effect and spin-orbit interaction at the same time, and for the first time, systematic accuracy verification of SCDFT was performed on 35 kinds of elemental metals (including non-superconductors). From this verification, we found the following;
    (a) The spin fluctuation systematically reduces Tc of these elemental isotropic superconductors and improves the accuracy. This effect is more crucial in transition metals than in sp-electrons metals, and in particular, as it moves to 5d → 4d → 3d.
    (b) The effect of spin-orbit interaction is weak in many systems except Sn, Re, Tl, and Pb. The change in Tc due to this effect is not equal and may increase or decrease.
    (c) The non-superconductivity of noble metals, alkaline (earth) metals, and Sc can be reproduced.
    These results offered a way for the search for superconducting materials by high-throughput calculation and the strategies to improve SCDFT itself.
    The research results were published in Phys. Rev. B. This was conducted in collaboration with Tsuneyuki Research Group of department of Physics, The University of Tokyo. [2020/4/20]
    For more details, please see here.

Press Release

  • “Tokyo University developed a technique to accurately calculate metal, a semiconductor and an insulator.,
    Nikkan Kogyo, 2016/12/30
  • “Fujitsu Laboratories Ltd. has successfully simulated the electrical properties of a 3,000-atom nano device”,
    Nikkan Kogyo, 2014/1/14
  • “JAIST succeeded in Experimental Evidence for Epitaxial Silicene on Diboride Thin Films -”,
    Nikkan Kogyo, Kyodo News, The Kyoto Shimbun, Shikoku News, Oita Godo Shimbun, 2012/5/30
  • “Fujitsu Succeeds at Large-Scale Calculations Enabling the Computational Design of Novel Nanodevices”,
    Nihon Keizai Shimbun, 2011/8/8

Past News (Until May 2014 at JAIST)

  • The study entitled "Systematic study of electronic and magnetic properties for Cu12-xTMxSb4S13 (TM=Mn, Fe, Co, Ni, and Zn) tetrahedrite" was published in J. Appl. Phys. (Published online April 9). The research was conducted in collaboration with Dr. Suekuni of Hiroshima University and Prof. Koyano's group of JAIST. J. Appl. Phys. 115, 143702 (5 pages) (2014)
  • The study entitled "Microscopic origin of the π states in epitaxial silicene" from collaborative work of Takamura-Yamada group (School of Materials Science, JAIST), Hasegawa group (ISSP, Univ. Tokyo), and Ozaki group was published in Appl. Phys. Lett. (Published online January 16). Appl. Phys. Lett. 104, 021605 (4 pages) (2014)

Past Seminars (Until May 2014 at JAIST)
"Simulation Science" Seminars hosted by RCSS, JAIST

  • 8th Simulation Science Seminar
    • TITLE: Understanding the STM and AFM contrast in graphene, reducible oxides and biomolecules
    • SPEAKER: Ruben Perez (Professor, Theory of Condensed Matter Department, Universidad Autonoma de Madrid,
    • DATE/TIME: 2013 Nov. 18, 15:00-16:30
    • SUMMARY: We’ll review the computational tools and protocols developed in our group in order to study the mechanical and transport properties of materials, and its application to the understanding of the atomic-resolution images obtained with the scanning tunneling (STM) and the force microscope (AFM) by different experimental groups on technologically relevant materials. Firstly, we’ll focus on tuning of the electronic properties of graphene through the creation of defect and edge states, looking, in particular, to the connection of graphene with metal surfaces. Combining high resolution STM experiments and DFT calculations, we have unambiguously unveiled the atomic structure of the boundary between a graphene zigzag edge and a Pt(111) step. The graphene edges minimize their strain by inducing a 3-fold edge-reconstruction on the metal side. We have shown the existence of an unoccupied electronic state exclusively localized in the C-edge atoms of a particular graphene sublattice, which could be used to develop new dual-channel devices. Metal oxides play a key role in a wide range of technological applications. While in many cases the same FM-AFM image can be explained by different models, and even different underlying tip-sample interactions, we show here that the combination of force spectroscopy (FS) measurements and first-principles simulations can provide an unambiguous identification of the tip structure and the image contrast mechanism in rutile TiO2 (110) and anatase TiO2 (101) surfaces. In the case of STM, we have made a comprehensive study of the (2√2x√2)R45゜ missing row reconstruction of the Cu(100) surface, using different tips and systematically varying bias voltage and tip sample distance, to explore the rich variety of image contrasts observed in the experiments. Our results achieve a conclusive understanding of fundamental STM imaging mechanisms and provide guidelines for experimentalists to achieve chemically selective imaging by selecting imaging parameters. Finally, we’ll present our recent work on the structure and functionality of biological systems in their native liquid environment. We’ll discuss the application of large-scale steered Molecular Dynamics simulations, based on classical potentials developed by the molecular biology community and the use of GPUs as processing units, provide insight into the protein-graphene biocompatibility, the flexibility map of human antibodies, and the hydration properties of self-assembled monolayers of single-stranded DNA and its possible use as a label-free DNA sensor.