Akai Group

Project Professor

AKAI,Hisazumi

Our main objective is to theoretically produce new functionality materials by means of computational materials design (CMD). In particular, the development of new high-performance permanent magnets is one of our main targets. CMD aims at to design materials and/or structures on the basis of quantum mechanics. This corresponds to the inverse problem of quantum simulation. In general, solving such a problem is very difficult, but in the case of CMD we can solve this by making use of the knowledge, which is obtained through quantum simulations, about underlying mechanisms that realize a specific feature of materials. In this regards, the developments of new methods of quantum simulation are also our very important subjects. Among them are developments of methods of accurate first-principles electronic structure calculations in general, first-principles non-equilibrium Green’s function method, screened KKR-method that realizes exact order-N calculation for huge systems, and the methods beyond LDA.

ZnS doped with Cr and Fe is predicted to be a half-metallic antiferromagnet (compensated ferri-magnet) (HM-AF). Also we have predicted that many other intermetallic compounds such as CrFeS_{2} might be HM-AF.

The magnetic anisotropy energy (MAE) of a new type of magnet Sm_{2}Fe_{17}N_{x}. The experimental observation that MAE changes its sign from in-plane to uniaxial anisotropy, which is necessary for permanent magnets, is correctly reproduced by our first-principles calculation.

- First-principles electronic structure calculation
- Computational materials design (CMD)
- KKR Green's function method and its applications
- Magnetism and development of new permanent magnets

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Relevance of 4f-3d exchange to finite-temperature magnetism of rare-earth permanent magnets: An ab-initio-based spin model approach for NdFe_{12}N: M. Matsumoto, H. Akai, Y. Harashima, S. Doi and T. Miyake, J. Appl. Phys. **119** (2016) 213901-1-7.

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Ab initio study of ^{59}Co NMR spectra in Co_{2}FeAl_{1−x}Si_{x} Heusler alloys: H. Nishihara, K. Sato, H. Akai, C. Takiguchi, M. Geshi, T. Kanomata, T. Sakon and T. Wada, Physica B **485** (2015) 66-70.

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Near-field correction in the first-principles calculations by the exact two-center expansion for the inverse of the distance: M. Ogura, C. Zecha, M. Offenberger, H. Ebert and H. Akai, J. Phys.: Condens. Matter **27** (2015) 485201-1-8.

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Optimized effective potential method and application to a static RPA correlation: T. Fukazawa and H. Akai, J. Phys.: Condens. Matter **27** (2015) 115502-1-10.

^{*} Joint research between groups within ISSP.