研究者詳細 - 旭　良司

論文 - 旭　良司

分割表示 >> ／全件表示 170 件中 1 - 170 件目

Enhancing fluoride-ion conduction via doping-induced anionic ordering in an n = 1 Ba-based Ruddlesden-Popper oxyfluoride structure 査読有り

Chanachai Pattanathummasid, Ryoji Asahi, Alex Kutana, Kazuhiro Mori, Toshiyuki Matsunaga, Tsuyoshi Takami

Solid State Ionics 424 巻頁： 116866 2025年4月

Polyvalent machine-learned potential for cobalt: From bulk to nanoparticles 査読有り国際共著

Marthe Bideault, Jérôme Creuze, Ryoji Asahi, Erich Wimmer

Physical Review Materials 8 巻頁： 123803 2024年12月

Realization of Ideal Ba Promoter State by Simultaneous Incorporation with Co into Carbon-protective Framework for Ammonia Synthesis Catalyst 査読有り

K. Kanishka H. De Silva, Katsutoshi Sato, Takahiro Naito, Takaaki Toriyama, Tomokazu Yamamoto, Ryotaro Aso, Yasukazu Murakami, Pradeep R. Varadwaj, Ryoji Asahi, Koji Inazu, Katsutoshi Nagaoka

Advanced Energy Materials 頁： 2404030 2024年12月

Roadmap on methods and software for electronic structure based simulations in chemistry and materials 招待有り査読有り国際共著

Volker Blum, Ryoji Asahi et al.

Electronic Structure 6 巻 ( 4 ) 頁： 042501 2024年11月

Topochemical Fluoride Exchange Reaction with Anionic Electrons toward Fluoride-Ion Conduction in Layered Ba2–xAxNF1–x (A = Na, K) 査読有り

Chanachai Pattanathummasid, Nozomu Yasufuku, Ryoji Asahi, Alex Kutana, Masato Hagihara, Kazuhiro Mori, and Tsuyoshi Takami

Chemistry of Materials 36 巻 ( 11 ) 頁： 5671 - 5677 2024年5月

Machine learning and atomistic origin of high dielectric permittivity in oxides. 査読有り

Shimano Y, Kutana A, Asahi R

Scientific reports 13 巻 ( 1 ) 頁： 22236 2023年12月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（その他学術会議資料等）出版者・発行元：Scientific Reports

Discovering new stable materials with large dielectric permittivity is important for future energy storage and electronics applications. Theoretical and computational approaches help design new materials by elucidating microscopic mechanisms and establishing structure–property relations. Ab initio methods can be used to reliably predict the dielectric response, but for fast materials screening, machine learning (ML) approaches, which can directly infer properties from the structural information, are needed. Here, random forest and graph convolutional neural network models are trained and tested to predict the dielectric constant from the structural information. We create a database of the dielectric properties of oxides and design, train, and test the two ML models. Both approaches show similar performance and can successfully predict response based on the structure. The analysis of the feature importance allows identification of local geometric features leading to the high dielectric permittivity of the crystal. Dimensionality reduction and clustering further confirms the relevance of descriptors and compositional features for obtaining high dielectric permittivity.

DOI： 10.1038/s41598-023-49603-2

Scopus

PubMed

Molecular dynamics simulations using machine learning potential for a-Si:H/c-Si interface: Effects of oxygen and hydrogen on interfacial defect states 招待有り査読有り国際共著

Semba, T; Mckibbin, J; Jinnouchi, R; Asahi, R

JOURNAL OF MATERIALS RESEARCH ( 38 ) 頁： 5151 - 5160 2023年9月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（その他学術会議資料等）出版者・発行元：Journal of Materials Research

Molecular dynamics simulations of a-Si:H/c-Si models with and without an oxygen layer at the interface were performed using a machine learning potential (MLP) that was efficiently trained using an on-the-fly scheme with ab initio molecular dynamics. The relaxation processes up to 1 ns at 500 and 700 K were simulated using MLP, and snapshots were evaluated using ab initio calculations to examine the in-gap states that could significantly affect the solar cell performance. The results showed that oxygen atoms passivated surface dangling bonds on c-Si, but simultaneously generated strain-induced in-gap states at the Si–O/a-Si interface. The hydrogen atoms suppressed the recrystallization of a-Si, distributed in a-Si particularly at the Si–O/a-Si interface because of the repulsive potential of the Si–O layer and contributed to the reduction of the in-gap states. Our results support experimental observation where optimization of the a-Si:H/O/c-Si interface could improve the performance of solar cells. Graphical abstract: [Figure not available: see fulltext.]

DOI： 10.1557/s43578-023-01155-x

Web of Science

Scopus

Polymorphs of Titanium Dioxide: An Assessment of the Variants of Projector Augmented Wave Potential of Titanium on Their Geometric and Dielectric Properties 査読有り

Pradeep R. Varadwaj, Van An Dinh, Yoshitada Morikawa, Ryoji Asahi

ACS Omega 8 巻 ( 24 ) 頁： 220003 - 22017 2023年6月

Automatic knowledge acquisition from superconductivity information in literature 査読有り

Kento Mitsui, Yutaka Sasaki, Ryoji Asahi

Science and Technology of Advanced Materials: Methods 3 巻頁： 2206532 2023年5月

Challenges for fluoride superionic conductors: fundamentals, design, and applications 招待有り査読有り

Tsuyoshi Takami, Chanachai Pattanathummasid, Alex Kutana, Ryoji Asahi

Journal of Physics: Condensed Matter 35 巻頁： 293002 2023年4月

Permittivity boosting by induced strain from local doping in titanates from first principles 査読有り

A. Kutana, Y. Shimano, R. Asahi

Scientific Reports 13 巻頁： 3761 2023年3月

Ultrafast charge-transfer dynamics in a visible-light-excited iridium(III) terpyridine 2-phenylpyridine complex studied by femtosecond X-ray absorption spectroscopy 査読有り国際共著

K. Yamanaka, T. Morikawa, R. Asahi

JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY 435 巻頁： 114267 2023年2月

Superconductivity information extraction from the literature: A new corpus and its evaluations 査読有り

Kyosuke Yamaguchi, Ryoji Asahi, Yutaka Sasaki

Advanced Engineering Informatics 54 巻頁： 101768 2022年10月

See d-assiste d epitaxy of intermetallic compounds with interface-determined orientation: Incommensurate Nowotny chimney-ladder FeGe? epitaxial film 査読有り

Terada Tsukasa, Kitaura Reona, Ishigaki Shintaro, Ishibe Takafumi, Naruse Nobuyasu, Mera Yutaka, Asahi Ryoji, Nakamura Yoshiaki

ACTA MATERIALIA 236 巻 2022年9月

Doping Effect and Li-Ion Conduction Mechanism of ALi<inf>6</inf>XO<inf>6</inf>(A = K or Rb and X = Pentavalent): A First-Principles Study 査読有り

Lee J., Asahi R.

Journal of Physical Chemistry C 126 巻 ( 32 ) 頁： 13548 - 13559 2022年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physical Chemistry C

Recent theoretical and experimental evaluations demonstrated that KLi6TaO6 is a good Li-ion conductor. In this study, the energetics and detailed mechanism of Li-ion migration, relevant to the point defects of KLi6TaO6, were analyzed by first-principles calculations. Defect formation energy analysis suggested that it has limited chemical potential conditions for attaining Li-excess conditions through doping (substituting tetravalent elements for Ta). The formation of other native defects, such as Li vacancies, hinders the stabilization of the dopant and compensates for the interstitial Li. When the doping is successful, the interactions between the coexisting dopant and interstitial Li can increase the migration energy barrier of the interstitial Li. This phenomenon limits the factors responsible for achieving high Li-ion conductivity in this material. Based on the results of the investigations on KLi6TaO6, isostructural materials of the form ALi6XO6, with various combinations of constituent elements A and X, were each screened on the basis of high stability and low Li-ion migration energy. Twelve structures of the form (A = K or Rb)Li6XO6 were suggested, of which X was pentavalent. They also exhibited limited chemical potential conditions for achieving Li-excess conditions through doping. Combinations of the suggested isostructural oxides and dopants were identified to reduce the interactions between interstitial Li and dopant. Some isostructural oxides were doped using Sn and were evaluated using first-principles molecular dynamics; their Li-ion conductivities at room temperature were found to be comparable with those of garnet-type Li-ion conductors.

DOI： 10.1021/acs.jpcc.2c02357

Scopus

Theoretical and Experimental Studies of KLi6TaO6 as a Li-Ion Solid Electrolyte 査読有り

Suzuki Nobuaki, Lee Joohwi, Masuoka Yumi, Ohta Shingo, Kobayashi Tetsuro, Asahi Ryoji

INORGANIC CHEMISTRY 60 巻 ( 14 ) 頁： 10371 - 10379 2021年7月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（その他学術会議資料等）出版者・発行元：Inorganic Chemistry

We study a hexagonal oxide KLi6TaO6 (KLTO), proposed as a Li-ion solid electrolyte, by using a recently developed screening method. First-principles calculations predict that KLTO presents a good Li-ion conductivity (σLi) and a low activation energy (Ea). Li migration is enhanced by the presence of excess Li ions in the interstitial region via a kick-out mechanism. Our experimental results demonstrate that Sn-doped KLTO presents a conductivity of 1 × 10-5 S cm-1, a σLi of 6 × 10-6 S cm-1, and a relatively low Ea of 36 kJ mol-1, which confirm the validity of the proposed screening method. Conversely, detailed analyses of the microstructure and X-ray diffraction patterns of KLTO samples indicate that a stable Li-excess condition is not achieved, therefore leaving potential improvement of the performance of KLTO as a Li-ion solid electrolyte by optimizing extrinsic doping and fabrication processes.

DOI： 10.1021/acs.inorgchem.1c00902

Web of Science

Scopus

PubMed

Transfer learning for materials informatics using crystal graph convolutional neural network 査読有り

Lee Joohwi, Asahi Ryoji

COMPUTATIONAL MATERIALS SCIENCE 190 巻 2021年4月

Molecular dynamics simulations of lithium superionic conductor Li<inf>10</inf>GeP<inf>2</inf>S<inf>12</inf> using a machine learning potential 査読有り

Miwa Kazutoshi, Asahi Ryoji

Solid State Ionics 361 巻 2021年3月

Characterization of AE(TM)(2)Bi2O9 (AE: Ca, Sr, Ba; TM: Nb, Ta) as oxide ion conductors 査読有り

Tajima Shin, Ohba Nobuko, Suzumura Akitoshi, Masuoka Yumi, Asahi Ryoji

JOURNAL OF THE EUROPEAN CERAMIC SOCIETY 41 巻 ( 2 ) 頁： 1352 - 1359 2021年2月

Stationary interatomic force constant matrix method with ultrasoft pseudopotentials 査読有り

Miwa Kazutoshi, Asahi Ryoji

PHYSICAL REVIEW B 102 巻 ( 17 ) 2020年11月

On-the-Fly Active Learning of Interatomic Potentials for Large-Scale Atomistic Simulations 査読有り

Jinnouchi Ryosuke, Miwa Kazutoshi, Karsai Ferenc, Kresse Georg, Asahi Ryoji

JOURNAL OF PHYSICAL CHEMISTRY LETTERS 11 巻 ( 17 ) 頁： 6946 - 6955 2020年9月

Charge Trapping Process in Photoexcited Nitrogen-Doped Titanium Oxides 査読有り

Sato Kosuke, Yamanaka Ken-ichi, Nozawa Shunsuke, Fukuzawa Hironobu, Katayama Tetsuo, Morikawa Takeshi, Nonaka Takamasa, Dohmae Kazuhiko, Ueda Kiyoshi, Yabashi Makina, Asahi Ryoji

INORGANIC CHEMISTRY 59 巻 ( 15 ) 頁： 10439 - 10449 2020年8月

Descriptors representing two- and three-body atomic distributions and their effects on the accuracy of machine-learned inter-atomic potentials 査読有り

Jinnouchi Ryosuke, Karsai Ferenc, Verdi Carla, Asahi Ryoji, Kresse Georg

JOURNAL OF CHEMICAL PHYSICS 152 巻 ( 23 ) 頁： 234102 2020年6月

Discovery of superionic conductors by ensemble-scope descriptor 査読有り

Kajita Seiji, Ohba Nobuko, Suzumura Akitoshi, Tajima Shin, Asahi Ryoji

NPG ASIA MATERIALS 12 巻 ( 1 ) 2020年4月

Design Rules for High Oxygen-Ion Conductivity in Garnet-Type Oxides 査読有り

Lee Joohwi, Ohba Nobuko, Asahi Ryoji

CHEMISTRY OF MATERIALS 32 巻 ( 4 ) 頁： 1358 - 1370 2020年2月

Identifying superionic conductors by materials informatics and high-throughput synthesis 査読有り

Matsubara Masato, Suzumura Akitoshi, Ohba Nobuko, Asahi Ryoji

COMMUNICATIONS MATERIALS 1 巻 ( 1 ) 2020年2月

SC-CoMIcs: A superconductivity corpus for materials informatics 査読有り

Yamaguchi K., Asahi R., Sasaki Y.

LREC 2020 - 12th International Conference on Language Resources and Evaluation, Conference Proceedings 頁： 6753 - 6760 2020年

Atomistic Modeling of Photoelectric Cells for Artificial Photosynthesis 査読有り

Asahi Ryoji, Jinnouchi Ryosuke

MULTISCALE SIMULATIONS FOR ELECTROCHEMICAL DEVICES 頁： 107 - 145 2020年

Multiscale Simulations for Electrochemical Devices Preface 査読有り

Asahi Ryoji

MULTISCALE SIMULATIONS FOR ELECTROCHEMICAL DEVICES 頁： XI - XIV 2020年

Highly efficient evaluation of diffusion networks in Li ionic conductors using a 3D-corrugation descriptor 査読有り

France-Lanord Arthur, Asahi Ryoji, Leblanc Benoit, Lee Joohwi, Wimmer Erich

SCIENTIFIC REPORTS 9 巻 ( 1 ) 頁： 15123 2019年10月

y Path integral study on C15-type Laves TiCr2 hydride 査読有り

Miwa Kazutoshi, Asahi Ryoji

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 44 巻 ( 42 ) 頁： 23708 - 23715 2019年9月

Phosphorescent Material Search Using a Combination of High-Throughput Evaluation and Machine Learning 査読有り

Hazama Hirofumi, Sobue Susumu, Tajima Shin, Asahi Ryoji

INORGANIC CHEMISTRY 58 巻 ( 16 ) 頁： 10936 - 10943 2019年8月

Development of a High-Throughput Screening Method for Oxide-Ion Conductors and Its Application to Bismuth-Based Oxide Library Thin Films 査読有り

Matsubara Masato, Suzumura Akitoshi, Tajima Shin, Asahi Ryoji

ACS COMBINATORIAL SCIENCE 21 巻 ( 5 ) 頁： 400 - 407 2019年5月

Water Facilitated Electrochemical Reduction of CO2 on Cobalt-Porphyrin Catalysts 査読有り

Miyamoto Kaito, Asahi Ryoji

JOURNAL OF PHYSICAL CHEMISTRY C 123 巻 ( 15 ) 頁： 9944 - 9948 2019年4月

Hybrid Quantum-Classical Simulation of Li Ion Dynamics and the Decomposition Reaction of Electrolyte Liquid at a Negative-Electrode/Electrolyte Interface 査読有り

Ohba Nobuko, Ogata Shuji, Asahi Ryoji

JOURNAL OF PHYSICAL CHEMISTRY C 123 巻 ( 15 ) 頁： 9673 - 9679 2019年4月

Collaborative effects of Zn and Sb Co-doping in magnesium silicide for thermoelectric applications 査読有り

Masuoka Yumi, Mito Youhiko, Ogino Atsushi, Nakamura Takashi, Amano Kumi, Asahi Ryoji

JOURNAL OF ALLOYS AND COMPOUNDS 781 巻頁： 606 - 612 2019年4月

First-principles prediction of high oxygen-ion conductivity in trilanthanide gallates Ln(3)GaO(6) 査読有り

Lee Joohwi, Ohba Nobuko, Asahi Ryoji

SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 20 巻 ( 1 ) 頁： 144 - 159 2019年3月

Correlation between thermal-vibration-induced large displacement of Cu atoms and phase transition in Cu4SnS4: First-principles investigation 査読有り

Nagasako Naoyuki, Suzumura Akitoshi, Asahi Ryoji

ACTA MATERIALIA 166 巻頁： 37 - 46 2019年3月

Oxygen conduction mechanism in Ca3Fe2Ge3O12 garnet-type oxide 査読有り

Lee Joohwi, Ohba Nobuko, Asahi Ryoji

SCIENTIFIC REPORTS 9 巻 ( 1 ) 頁： 2593 2019年2月

Effects of doping IIIB elements (Al, Ga, In) on thermoelectric properties of nanostructured n-type filled skutterudite compounds 査読有り

Matsubara M., Masuoka Y., Asahi R.

JOURNAL OF ALLOYS AND COMPOUNDS 774 巻頁： 731 - 738 2019年2月

Solar Thermal Cogeneration System Using a Cylindrical Thermoelectric Module 査読有り

Suzumura Akitoshi, Hazama Hirofumi, Matsubara Masato, Asahi Ryoji

JOURNAL OF ELECTRONIC MATERIALS 48 巻 ( 1 ) 頁： 467 - 474 2019年1月

Molecular dynamics simulations with machine learning potential for Nb-doped lithium garnet-type oxide Li7-xLa3(Zr2-xNbx)O-12 査読有り

Miwa Kazutoshi, Asahi Ryoji

PHYSICAL REVIEW MATERIALS 2 巻 ( 10 ) 2018年10月

Charge transfer dynamics at the boron subphthalocyanine chloride/C-60 interface: non-adiabatic dynamics study with Libra-X 査読有り

Sato Kosuke, Pradhan Ekadashi, Asahi Ryoji, Akimov Alexey V.

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 20 巻 ( 39 ) 頁： 25275 - 25294 2018年10月

Cylindrical thermoelectric generator with water heating system for high solar energy conversion efficiency 査読有り

Hazama Hirofumi, Masuoka Yumi, Suzumura Akitoshi, Matsubara Masato, Tajima Shin, Asahi Ryoji

APPLIED ENERGY 226 巻頁： 381 - 388 2018年9月

Phase-field modeling of stress generation in polycrystalline LiCoO2 査読有り

Yamakawa Shunsuke, Nagasako Naoyuki, Yarnasaki Hisatsugu, Koyama Toshiyuki, Asahi Ryoji

SOLID STATE IONICS 319 巻頁： 209 - 217 2018年6月

Band bending and dipole effect at interface of metal-nanoparticles and TiO2 directly observed by angular-resolved hard X-ray photoemission spectroscopy 査読有り

Sato Shunsuke, Kataoka Keita, Jinnouchi Ryosuke, Takahashi Naoko, Sekizawa Keita, Kitazumi Kousuke, Ikenaga Eiji, Asahi Ryoji, Morikawa Takeshi

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 20 巻 ( 16 ) 頁： 11342 - 11346 2018年4月

Effects of Ta2O5 Surface Modification by NH3 on the Electronic Structure of a Ru-Complex/N Ta2O5 Hybrid Photocatalyst for Selective CO2 Reduction 査読有り

Shirai Soichi, Sato Shunsuke, Suzuki Tomiko M., Jinnouchi Ryosuke, Ohba Nobuko, Asahi Ryoji, Morikawa Takeshi

JOURNAL OF PHYSICAL CHEMISTRY C 122 巻 ( 4 ) 頁： 1921 - 1929 2018年2月

Discovery of zirconium dioxides for the design of better oxygen-ion conductors using efficient algorithms beyond data mining 査読有り

Lee Joohwi, Ohba Nobuko, Asahi Ryoji

RSC ADVANCES 8 巻 ( 45 ) 頁： 25534 - 25545 2018年

電子顕微鏡像からのイオン伝導度の学習 ~畳み込みニューラルネットワークによる特徴可視化~ 査読有り

近藤瑠歩, 山川俊輔, 増岡優美, 田島伸, 旭良司

人工知能学会全国大会論文集 2018 巻 ( 0 ) 頁： 3Z103 - 3Z103 2018年

担当区分：最終著者記述言語：日本語掲載種別：研究論文（その他学術会議資料等）出版者・発行元：一般社団法人人工知能学会

本研究では，畳み込みニューラルネットワーク（CNN）を用いて材料の物性予測に必要な特徴を微視組織から自動的に抽出することを試みた．まず，実験で得られた電子顕微鏡像およびイオン伝導度を訓練データとして用いてCNNを訓練した．次に，訓練後のCNNに電子顕微鏡像を入力した際のGlobal Average Pooling（GAP）レイヤー直後の発火と，与えた電子顕微鏡像の教師データ（イオン伝導度）との相関を調べ，正（負）の相関のあるものを高（低）イオン伝導体に特有の特徴と定義した．それぞれの特徴のGAP適用前の特徴マップを比較したところ，結晶欠陥の少ない領域および径の大きなボイドが高イオン伝導体に特有の特徴であり，径の小さなボイドが低イオン伝導体に特有の特徴であることが分かった．この知見は材料技術者の持つ知識と一致しており，CNNによる特徴の自動抽出が有効であることを示すことができた．

DOI： 10.11517/pjsai.JSAI2018.0_3Z103

実験スペクトル自動分解のための線形独立非負行列因子分解法の提案査読有り

吉川信明, 鈴村彰敏, 田島伸, 山川俊輔, 旭良司

人工知能学会全国大会論文集 2018 巻 ( 0 ) 頁： 3Z101 - 3Z101 2018年

担当区分：最終著者記述言語：日本語掲載種別：研究論文（その他学術会議資料等）出版者・発行元：一般社団法人人工知能学会

高速X線測定で得られる多数のXRDスペクトルを単相スペクトルに分解する手法として、線形独立性を考慮した非負値行列因子分解法を提案する。本手法では線形独立性を定量化し、これを非負値行列因子分解の正則化項として利用している。手法自体は非常に簡便ではあるが、本手法により分解されたスペクトルは実際の単相スペクトルとよい一致を示した。これは線形独立性という概念が単相スペクトルの特徴をよく捉えていることを意味する。本手法ではデータベースの参照は行わないため、本手法を用いることで未知の結晶相を発見できる可能性がある。

DOI： 10.11517/pjsai.JSAI2018.0_3Z101

固体系材料インフォマティクスのための畳み込みニューラルネットを活用する3Dボクセルデータ記述子査読有り

梶田晴司, 大庭伸子, 旭良司

人工知能学会全国大会論文集 2018 巻 ( 0 ) 頁： 3Z102 - 3Z102 2018年

担当区分：最終著者記述言語：日本語掲載種別：研究論文（その他学術会議資料等）出版者・発行元：一般社団法人人工知能学会

マテリアルズ・インフォマティクス（MI）は、従来は膨大なコストをかけていた材料探索を、データサイエンスのアプローチから材料探索を加速させる取り組みである。分子系MIと異なり固体系MIの事例は非常に少ない。その理由の一つは、電子やポテンシャルといった結晶全体に広がる３次元の場の量を精確に表現する記述子がないためだ。本研究では、畳み込みニューラルネットを活用してこの３次元の場の量を表現する、逆格子３Dボクセル空間記述子を開発した。680種類の酸化物に対してパフォーマンスを測定したところ、場の量に関連する物理量の回帰精度は従来の記述子の予測精度を超えることが分かった。

DOI： 10.11517/pjsai.JSAI2018.0_3Z102

A Universal 3D Voxel Descriptor for Solid-State Material Informatics with Deep Convolutional Neural Networks 査読有り

Kajita Seiji, Ohba Nobuko, Jinnouchi Ryosuke, Asahi Ryoji

SCIENTIFIC REPORTS 7 巻 ( 1 ) 頁： 16991 2017年12月

Improvement of power factor of n-type Bi2Te3 by dispersed nanosized Ga2Te3 precipitates 査読有り

Hazama Hirofumi, Masuoka Yumi, Yamamoto Hidenari, Suto Hiroyuki, Kinoshita Yohei, Ishikiriyama Mamoru, Asahi Ryoji

JOURNAL OF ALLOYS AND COMPOUNDS 726 巻頁： 578 - 586 2017年12月

Microstructure recognition using convolutional neural networks for prediction of ionic conductivity in ceramics 査読有り

Kondo Ruho, Yamakawa Shunsuke, Masuoka Yumi, Tajima Shin, Asahi Ryoji

ACTA MATERIALIA 141 巻頁： 29 - 38 2017年12月

Extrapolating Energetics on Clusters and Single-Crystal Surfaces to Nanoparticles by Machine-Learning Scheme 査読有り

Jinnouchi Ryosuke, Hirata Hirohito, Asahi Ryoji

JOURNAL OF PHYSICAL CHEMISTRY C 121 巻 ( 47 ) 頁： 26397 - 26405 2017年11月

Study of the conformation of polyelectrolyte aggregates using coarse-grained molecular dynamics simulations 査読有り

Mima Toshiki, Kinjo Tomoyuki, Yamakawa Shunsuke, Asahi Ryoji

SOFT MATTER 13 巻 ( 35 ) 頁： 5991 - 5999 2017年9月

Predicting Catalytic Activity of Nanoparticles by a DFT-Aided Machine-Learning Algorithm 査読有り

Jinnouchi Ryosuke, Asahi Ryoji

JOURNAL OF PHYSICAL CHEMISTRY LETTERS 8 巻 ( 17 ) 頁： 4279 - 4283 2017年9月

Measurement and ab initio calculation of the structural parameters and physical properties of 3d transition intermetallics TiMP (M = Cr, Mn, Fe, Co, or Ni) 査読有り

Suzuki Nobuaki, Asahi Ryoji, Kishida Yoshihiro, Masuoka Yumi, Sugiyama Jun

MATERIALS RESEARCH EXPRESS 4 巻 ( 4 ) 2017年4月

畳み込みニューラルネットワークを用いたセラミックス材料組織からのイオン伝導予測

近藤瑠歩, 山川俊輔, 増岡優美, 田島伸, 旭良司

計算力学講演会講演論文集 2017 巻 ( 0 ) 2017年

Optimization of Filler Elements in CoSb3-Based Skutterudites for High-Performance n-Type Thermoelectric Materials 査読有り

Matsubara M., Asahi R.

JOURNAL OF ELECTRONIC MATERIALS 45 巻 ( 3 ) 頁： 1669 - 1678 2016年3月

Microscopic study of gum-metal alloys: A role of trace oxygen for dislocation-free deformation 査読有り

Nagasako Naoyuki, Asahi Ryoji, Isheim Dieter, Seidman David N., Kuramoto Shigeru, Furuta Tadahiko

ACTA MATERIALIA 105 巻頁： 347 - 354 2016年2月

Transport properties of the Cu2ZnSnS4 bulk systems: Effects of nonstoichiometry and defect formation 査読有り

Hazama Hirofumi, Tajima Shin, Masuoka Yumi, Asahi Ryoji

JOURNAL OF ALLOYS AND COMPOUNDS 657 巻頁： 179 - 183 2016年2月

Upward Shift in Conduction Band of Ta2O5 Due to Surface Dipoles Induced by N-Doping 査読有り

Jinnouchi Ryosuke, Akimov Alexey V., Shirai Soichi, Asahi Ryoji, Prezhdo Oleg V.

JOURNAL OF PHYSICAL CHEMISTRY C 119 巻 ( 48 ) 頁： 26925 - 26936 2015年12月

Sodium distribution in solar-grade Cu2ZnSnS4 layers using atom-probe tomographic technique 査読有り

Tajima Shin, Asahi Ryoji, Isheim Dieter, Seidman David N., Itoh Tadayoshi, Ohishi Kei-ichiro

JAPANESE JOURNAL OF APPLIED PHYSICS 54 巻 ( 11 ) 2015年11月

Thermal diffusion of correlated Li-ions in graphite: A hybrid quantum-classical simulation study 査読有り

Ohba Nobuko, Ogata Shuji, Kouno Takahisa, Asahi Ryoji

COMPUTATIONAL MATERIALS SCIENCE 108 巻頁： 250 - 257 2015年10月

What Makes the Photocatalytic CO2 Reduction on N-Doped Ta2O5 Efficient: Insights from Nonadiabatic Molecular Dynamics 査読有り

Akimov Alexey V., Asahi Ryoji, Jinnouchi Ryosuke, Prezhdo Oleg V.

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 137 巻 ( 35 ) 頁： 11517 - 11525 2015年9月

Improvement of the open-circuit voltage of Cu2ZnSnS4 solar cells using a two-layer structure 査読有り

Tajima Shin, Itoh Tadayoshi, Hazama Hirofumi, Ohishi Keiichiro, Asahi Ryoji

APPLIED PHYSICS EXPRESS 8 巻 ( 8 ) 2015年8月

Theoretical Insights into the Impact of Ru Catalyst Anchors on the Efficiency of Photocatalytic CO2 Reduction on Ta2O5 査読有り

Akimov Alexey V., Jinnouchi R., Shirai S., Asahi R., Prezhdo Oleg V.

JOURNAL OF PHYSICAL CHEMISTRY B 119 巻 ( 24 ) 頁： 7186 - 7197 2015年6月

Highly luminescent flexible amino-functionalized graphene quantum dots@cellulose nanofiber-clay hybrids for white-light emitting diodes 査読有り

Tetsuka H., Nagoya A., Asahi R.

JOURNAL OF MATERIALS CHEMISTRY C 3 巻 ( 15 ) 頁： 3536 - 3541 2015年

Presence of a Doubly-Splitting Site and Its Effect on Thermoelectric Properties of Cu4SnS4 査読有り

Suzumura Akitoshi, Nagasako Naoyuki, Kinoshita Youhei, Watanabe Masaki, Kita Takuji, Asahi Ryoji

MATERIALS TRANSACTIONS 56 巻 ( 6 ) 頁： 858 - 863 2015年

記述言語：英語掲載種別：研究論文（その他学術会議資料等）出版者・発行元：Materials Transactions

Thermoelectric properties of Cu4SnS4 significantly change around 230 K along with a phase transition between a high temperature phase (HT-phase) and a low temperature phase (LT-phase). Here we particularly focus on a very low thermal conductivity of Cu4SnS4, which is even lower in HT-phase. The crystal structures of Cu4SnS4 are analyzed using synchrotron radiation. HT-phase is determined to be orthorhombic structure with the space group Pnma, as previously reported; however, the results of Rietveld refinement of HT-phase suggest that there are some Cu sites around saddle points of the double well potential. Phonon dispersion calculated by first-principles calculations indeed exhibits soft phonon modes of the Cu sites, consistent with the Rietveld analysis. The detailed analysis leads to a conclusion that the lower thermal conductivity in HT-phase results from an additional phonon scattering resonated with an anharmonic Cu vibration in the double well potential.

DOI： 10.2320/matertrans.E-M2015804

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Scopus

059 放電過程におけるLi電池正極材料内の応力状態評価

山川俊輔, 長廻尚之, 山崎久嗣, 旭良司, 小山敏幸

計算力学講演会講演論文集 2015 巻 ( 0 ) 頁： _059 - 1_-_059-2_ 2015年

Nitrogen-Doped Titanium Dioxide as Visible-Light-Sensitive Photocatalyst: Designs, Developments, and Prospects 査読有り

Asahi Ryoji, Morikawa Takeshi, Irie Hiroshi, Ohwaki Takeshi

CHEMICAL REVIEWS 114 巻 ( 19 ) 頁： 9824 - 9852 2014年10月

Thermal expansion, diffusion and melting of Li2O using a compact forcefield derived from ab initio molecular dynamics 査読有り

Asahi Ryoji, Freeman Clive M., Saxe Paul, Wimmer Erich

MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING 22 巻 ( 7 ) 2014年10月

Atom-probe tomographic study of interfaces of Cu2ZnSnS4 photovoltaic cells 査読有り

Tajima S., Asahi R., Isheim D., Seidman D. N., Itoh T., Hasegawa M., Ohishi K.

APPLIED PHYSICS LETTERS 105 巻 ( 9 ) 2014年9月

Effect of microstructure on discharge properties of polycrystalline LiCoO2 査読有り

Yamakawa Shunsuke, Yamasaki Hisatsugu, Koyama Toshiyuki, Asahi Ryoji

SOLID STATE IONICS 262 巻頁： 56 - 60 2014年9月

Improvement in Thermoelectric Properties of Se-Free Cu3SbS4 Compound 査読有り

Suzumura Akitoshi, Watanabe Masaki, Nagasako Naoyuki, Asahi Ryoji

JOURNAL OF ELECTRONIC MATERIALS 43 巻 ( 6 ) 頁： 2356 - 2361 2014年6月

Surface segregations in platinum-based alloy nanoparticles 査読有り

Yamakawa Shunsuke, Asahi Ryoji, Koyama Toshiyuki

SURFACE SCIENCE 622 巻頁： 65 - 70 2014年4月

A metathesis reaction route to obtain fine Mg2Si particles 査読有り

Itahara H., Yamada T., Oh S. -Y., Asahi R., Imagawa H., Yamane H.

CHEMICAL COMMUNICATIONS 50 巻 ( 33 ) 頁： 4315 - 4318 2014年

Improvement of the open-circuit voltage of CU2ZnSnS4 cells using a two-layered process 査読有り

Tajima Shin, Itoh Tadayoshi, Hazama Hirofumi, Ohishi Keiichiro, Asahi Ryoji

2014 IEEE 40TH PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC) 頁： 431 - 434 2014年

Effects of viscosity, surface tension, and evaporation rate of solvent on dry colloidal structures: A lattice Boltzmann study 査読有り

Munekata Toshihisa, Suzuki Takahisa, Yamakawa Shunsuke, Asahi Ryoji

PHYSICAL REVIEW E 88 巻 ( 5 ) 頁： 052314 2013年11月

Phase-Field Modeling of Phase Transformations in Platinum-Based Alloy Nanoparticles 査読有り

Yamakawa Shunsuke, Asahi Ryoji, Koyama Toshiyuki

MATERIALS TRANSACTIONS 54 巻 ( 8 ) 頁： 1242 - 1249 2013年8月

記述言語：英語掲載種別：研究論文（その他学術会議資料等）出版者・発行元：Materials Transactions

A phase-field model that describes the phase decomposition and phase transformations inside platinum-based alloy nanoparticles is developed to elucidate the effects of particle size, alloy composition, and heat-treatment temperature on the microstructure formation. FePt, CoPt, NiPt, CuPt and IrPt binary alloy nanoparticles with diameters of less than 10 nm are investigated. The calculation results clearly show that surface segregation and atomic ordering are sensitive to the alloy components and particle size, and that the equilibrium nanostructure obtained varies according to the balance between the surface energy and chemical interaction between atomic components. Platinum-based alloy nanoparticles are expected to find applications as electrocatalysts in polymer electrolyte fuel cells. Thus, the proposed phase-field approach demonstrates its usefulness for the control of the radial distributions of each alloying component within a nanoparticle, leading to improvements in the activity and durability of the catalyst and reducing the required amount of platinum loading.

DOI： 10.2320/matertrans.ME201304

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Scopus

Numerical study of Li diffusion in polycrystalline LiCoO2 査読有り

Yamakawa Shunsuke, Yamasaki Hisatsugu, Koyama Toshiyuki, Asahi Ryoji

JOURNAL OF POWER SOURCES 223 巻頁： 199 - 205 2013年2月

1611 コバルト酸リチウム多結晶体におけるリチウムの有効拡散係数の推定

山川俊輔, 山崎久嗣, 井手一人, 旭良司, 小山敏幸

計算力学講演会講演論文集 2013 巻 ( 0 ) 頁： _1611 - 1_-_1611-2_ 2013年

2415 グラファイト中Li拡散に対するLi間相互作用の影響ハイブリッド量子古典シミュレーション

大庭伸子, 尾形修司, 河野貴久, 小林亮, 田村友幸, 旭良司

計算力学講演会講演論文集 2013 巻 ( 0 ) 頁： _2415 - 1_-_2415-2_ 2013年

記述言語：日本語掲載種別：研究論文（その他学術会議資料等）出版者・発行元：一般社団法人日本機械学会

LIイオン電池の負極にも実用化されているLI-グラファイト層間化合物に対して、我々はこれまでに、グラファイトの構造変化をりーズナブルな計算コストで取り入れることができるハイブリッド量子古典法を適用し、平均層間距離とLI拡散の関係、外部電場を用いたLI拡散の促進について報告した。本研究では、グラファイト中に複数のLIを配置し、L1拡散に対するL1間相互作用の影響を調べる。本研究におけるハイブリッドシミュレーションでは、LIとその周りの炭素原子を量子力学計算の対象とする量子領域とし、経験的相互作用モデルで記述される古典領域に埋め込む。量子力学計算には、大規模計算に対応できるよう開発した分割統治型実空間DFTコード(DC-RGDFT)を適用した。同一層間にLiC6の濃度で配置されたLIは熱拡散するが、cage効果により移動範囲が限定されること、初期に異なる層間で上下同じ位置に配置されたLIが、拡散時には互いの位置が重ならないよう、ずれていく様子を確認した。

DOI： 10.1299/jsmecmd.2013.26._2415-1_

Model GW study of the late transition metal monoxides 査読有り

Ye Lin-Hui, Asahi Ryoji, Peng Lian-Mao, Freeman Arthur J.

JOURNAL OF CHEMICAL PHYSICS 137 巻 ( 15 ) 頁： 154110 2012年10月

Optically Tunable Amino-Functionalized Graphene Quantum Dots 査読有り

Tetsuka Hiroyuki, Asahi Ryoji, Nagoya Akihiro, Okamoto Kazuo, Tajima Ichiro, Ohta Riichiro, Okamoto Atsuto

ADVANCED MATERIALS 24 巻 ( 39 ) 頁： 5333 - 5338 2012年10月

Thermoelectric Properties of Off-Stoichiometric Ti-Ni-Sn Half-Heusler Systems 査読有り

Hazama Hirofumi, Matsubara Masato, Asahi Ryoji

JOURNAL OF ELECTRONIC MATERIALS 41 巻 ( 6 ) 頁： 1730 - 1734 2012年6月

Enhanced Thermal Diffusion of Li in Graphite by Alternating Vertical Electric Field: A Hybrid Quantum-Classical Simulation Study 査読有り

Ohba Nobuko, Ogata Shuji, Tamura Tomoyuki, Kobayashi Ryo, Yamakawa Shunsuke, Asahi Ryoji

Journal of the Physical Society of Japan 81 巻 ( 2 ) 頁： 23601 - 23601 2012年2月

Enhanced Thermal Diffusion of Li in Graphite by Alternating Vertical Electric Field: A Hybrid Quantum-Classical Simulation Study 査読有り

Ohba Nobuko, Ogata Shuji, Tamura Tomoyuki, Kobayashi Ryo, Yamakawa Shunsuke, Asahi Ryoji

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 81 巻 ( 2 ) 2012年2月

Ideal tensile and shear strength of a gum metal approximant: Ab initio density functional calculations 査読有り

Nagasako Naoyuki, Asahi Ryoji, Hafner Juergen

PHYSICAL REVIEW B 85 巻 ( 2 ) 2012年1月

1111 フェーズフィールド法を用いた合金ナノ粒子内組成分布解析(OS11-4.フェーズフィールド法とその多様な展開(4),OS・一般セッション講演)

山川俊輔, 桜井清吾, 旭良司, 小山敏幸

計算力学講演会講演論文集 2012 巻 ( 0 ) 頁： 68 - 69 2012年

2110 DC-RGDFTを用いたハイブリッド量子古典シミュレーション : グラファイト中Li拡散への適用(OS21-3.固体物理/流体物理のマルチフィジックス/マルチスケール解析(3),OS・一般セッション講演)

大庭伸子, 尾形修司, 河野貴久, 小林亮, 田村友幸, 旭良司

計算力学講演会講演論文集 2012 巻 ( 0 ) 頁： 191 - 192 2012年

記述言語：日本語掲載種別：研究論文（その他学術会議資料等）出版者・発行元：一般社団法人日本機械学会

大規模計算に対応できるよう開発したオーダN型DC-RGDFTコードを量子力学計算に適用したハイブリッド量子古典シミュレーションにより、グラファイト中Li拡散に対するLi間相互作用の影響を調べた。グラファイト層内のLi間距離が10A以上離れている場合、Li間にグラファイトが2層以上含まれている場合には、それぞれのLiに対して独立に量子力学計算適用領域を設定した。近接して配置されたLiが互いの反発により拡散していく様子を確認した。

DOI： 10.1299/jsmecmd.2012.25.191

First-principles study of Cu2ZnSnS4 and the related band offsets for photovoltaic applications 査読有り

Nagoya A., Asahi R., Kresse G.

JOURNAL OF PHYSICS-CONDENSED MATTER 23 巻 ( 40 ) 2011年10月

A hybrid quantum-classical simulation study on stress-dependence of li diffusivity in graphite 査読有り

Ohba N.

CMES - Computer Modeling in Engineering and Sciences 75 巻 ( 3-4 ) 頁： 247 - 264 2011年9月

Improvement of thermoelectric properties for half-Heusler TiNiSn by interstitial Ni defects 査読有り

Hazama Hirofumi, Matsubara Masato, Asahi Ryoji, Takeuchi Tsunehiro

JOURNAL OF APPLIED PHYSICS 110 巻 ( 6 ) 2011年9月

Temperature-induced martensitic phase transitions in gum-metal approximants: First-principles investigations for Ti3Nb 査読有り

Lazar Petr, Jahnatek Michal, Hafner Juergen, Nagasako Naoyuki, Asahi Ryoji, Blaas-Schenner Claudia, Stoehr Markus, Podloucky Raimund

PHYSICAL REVIEW B 84 巻 ( 5 ) 2011年8月

計算材料設計を用いた熱電材料の開発査読有り

旭良司, 間広文, 長廻尚之, 松原賢東

セラミックス 46 巻 ( 6 ) 頁： 505 - 509 2011年6月

Fabrication of Nanocomposite Thermoelectric Materials by a Pulsed Laser Deposition Method 査読有り

Matsubara Masato, Azuma Hirozumi, Asahi Ryoji

JOURNAL OF ELECTRONIC MATERIALS 40 巻 ( 5 ) 頁： 1176 - 1180 2011年5月

Thermoelectric Properties of Si2Ti-Type Al-(Mn,Cr,Fe)-Si Alloys 査読有り

Toyama Yasuhiro, Hazama Hirofumi, Asahi Ryoji, Takeuchi Tsunehiro

JOURNAL OF ELECTRONIC MATERIALS 40 巻 ( 5 ) 頁： 1052 - 1056 2011年5月

A Hybrid Quantum-Classical Simulation Study on Stress-Dependence of Li Diffusivity in Graphite 査読有り

Ohba N., Ogata S., Tamura T., Yamakawa S., Asahi R.

CMES-COMPUTER MODELING IN ENGINEERING & SCIENCES 75 巻 ( 3-4 ) 頁： 247 - 265 2011年5月

1506 ハイブリッド量子古典シミュレーション : オーダーN型実空間DFT法の開発とLiグラファイト層間化合物への応用(OS15.固体物理/流体物理のマルチフィジックス/マルチスケール解析(2),OS・一般セッション講演)

大庭伸子, 尾形修司, 小林亮, 田村友幸, 旭良司

計算力学講演会講演論文集 2011 巻 ( 0 ) 頁： 481 - 482 2011年

906 フェーズフィールド法を用いた多結晶酸化物内リチウム拡散解析(OS9.フェーズフィールド法とその多様な展開(2),OS・一般セッション講演)

山川俊輔, 山崎久嗣, 小山敏幸, 旭良司

計算力学講演会講演論文集 2011 巻 ( 0 ) 頁： 296 - 297 2011年

Selected contributions from the 3rd Theory Meets Industry International Workshop, TMI2009 (Nagoya, Japan, 11-13 November 2009) PREFACE 査読有り

Tanaka Isao, Hafner Juergen, Wimmer Erich, Asahi Ryoji

JOURNAL OF PHYSICS-CONDENSED MATTER 22 巻 ( 38 ) 頁： 380301 2010年9月

Electronic Structure and Thermoelectric Properties of Al-Mn-Fe-Si Alloys 査読有り

Takeuchi T., Toyama Y., Hazama H., Asahi R.

JOURNAL OF ELECTRONIC MATERIALS 39 巻 ( 9 ) 頁： 1433 - 1438 2010年9月

Electronic structure and thermoelectric properties of Si<inf>2</inf>Ti-Type Al-(Mn, X)-Si (X = Cr, Fe) alloys 査読有り

Toyarna Y.

Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals 74 巻 ( 9 ) 頁： 605 - 609 2010年9月

記述言語：英語掲載種別：研究論文（その他学術会議資料等）出版者・発行元：Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals

In order to make variation in thermoelectric properties of Si2Ti-type Al32Mn34Si34, which possesses a large magnitude of Seebeck coefficient exceeding 300 μV/K, we partially substituted Fe and Cr for Mn, and succeeded in decreasing the number of valence electrons by the latter. The large, positive Seebeck coefficient up to 330 μV/K was observed for Al32CrxMn34−xSi34 (1≤x≤2.5), which consists almost solely of the phase of Si2Ti-type structure. The increase of hole concentration with increasing Cr concentration was confirmed by the fact that the electrical resistivity was decreased with Cr concentration. The positive sign and the decrease of Seebeck coefficient with increasing Cr concentration also lend a support on this scenario. The largest ZT-value with the positive sign of Seebeck coefficient (p-type behavior) was obtained at Al32Cr2.5Mn31.5Si34, and the resulting ZT-value was twice as large as the largest ZT-value of the ternary compound Al33Mn34Si33 that possesses a p-type behavior.

DOI： 10.2320/jinstmet.74.605

Scopus

Electronic Structure and Thermoelectric Properties of Si2Ti-Type Al-(Mn, X)-Si (X = Cr, Fe) Alloys 査読有り

Toyama Yasuhiro, Hazama Hirofumi, Asahi Ryoji, Takeuchi Tsunehiro

JOURNAL OF THE JAPAN INSTITUTE OF METALS 74 巻 ( 9 ) 頁： 605 - 609 2010年9月

Study of Electronic Structure and Defect Formation in Ti1-x Ni1+x Sn Half-Heusler Alloys 査読有り

Hazama Hirofumi, Asahi Ryoji, Matsubara Masato, Takeuchi Tsunehiro

JOURNAL OF ELECTRONIC MATERIALS 39 巻 ( 9 ) 頁： 1549 - 1553 2010年9月

Thermoelectric Properties of Si2Ti-Type Al-Mn-Si Alloys 査読有り

Takeuchi Tsunehiro, Toyama Yasuhiro, Yamamoto Akio, Hazama Hirofumi, Asahi Ryoji

MATERIALS TRANSACTIONS 51 巻 ( 6 ) 頁： 1127 - 1135 2010年6月

記述言語：英語掲載種別：研究論文（その他学術会議資料等）出版者・発行元：Materials Transactions

By using the first principle band calculations, we identified that Si2Ti-type Al-Mn-Si C54-phase possesses an electronic structure suitable for the thermoelectric materials. The formation range of the Al-Mn-Si C54-phase was determined by preparing samples at a number of different compositions, and the samples solely consisting of the C54-phase were successfully obtained around Al:Mn:Si=1:1:1. The carrier concentration of the Al-Mn-Si C54-phase was controlled by the partial substitution of the constituent elements, and behaviors in electrical properties characteristic to n-type and p-type thermoelectric materials were alternatively observed for the samples of a larger electron concentration and a smaller electron concentration, respectively. The absolute value of the Seebeck coefficient |S| was found to exceed 300 μV/K for both n-type and p-type samples.

DOI： 10.2320/matertrans.M2010022

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Scopus

Anomalies in the response of V, Nb, and Ta to tensile and shear loading: Ab initio density functional theory calculations 査読有り

Nagasako Naoyuki, Jahnatek Michal, Asahi Ryoji, Hafner Juergen

PHYSICAL REVIEW B 81 巻 ( 9 ) 2010年3月

Defect formation and phase stability of Cu2ZnSnS4 photovoltaic material 査読有り

Nagoya Akihiro, Asahi Ryoji, Wahl Roman, Kresse Georg

PHYSICAL REVIEW B 81 巻 ( 11 ) 2010年3月

Field-modulated thermopower in SrTiO3-based field-effect transistors with amorphous 12CaO center dot 7Al(2)O(3) glass gate insulator 査読有り

Ohta Hiromichi, Masuoka Yumi, Asahi Ryoji, Kato Takeharu, Ikuhara Yuichi, Nomura Kenji, Hosono Hideo

APPLIED PHYSICS LETTERS 95 巻 ( 11 ) 2009年9月

Preparation of Conducting Polyaniline-Bismuth Nanoparticle Composites by Planetary Ball Milling 査読有り

Anno H., Fukamoto M., Heta Y., Koga K., Itahara H., Asahi R., Satomura R., Sannomiya M., Toshima N.

JOURNAL OF ELECTRONIC MATERIALS 38 巻 ( 7 ) 頁： 1443 - 1449 2009年7月

Thermoelectric Properties of Organic Charge-Transfer Compounds 査読有り

Itahara H., Maesato M., Asahi R., Yamochi H., Saito G.

JOURNAL OF ELECTRONIC MATERIALS 38 巻 ( 7 ) 頁： 1171 - 1175 2009年7月

Cu2ZnSnS4 as a potential photovoltaic material: A hybrid Hartree-Fock density functional theory study 査読有り

Paier Joachim, Asahi Ryoji, Nagoya Akihiro, Kresse Georg

PHYSICAL REVIEW B 79 巻 ( 11 ) 2009年3月

e/a Determination for the transition metal element TM in Al-Cu-TM-Si (TM = Fe and Ru) approximants and B2-compounds by means of the FLAPW-Fourier method 査読有り

Mizutani Uichiro, Asahi Ryoji, Takeuchi Tsunehiro, Sato Hirokazu, Kontsevoi Oleg Y., Freeman Arthur J.

ZEITSCHRIFT FUR KRISTALLOGRAPHIE 224 巻 ( 1-2 ) 頁： 17 - 20 2009年

Failure of the Hume-Rothery stabilization mechanism in the Ag5Li8 gamma-brass studied by first-principles FLAPW electronic structure calculations 査読有り

Mizutani U., Asahi R., Sato H., Noritake T., Takeuchi T.

JOURNAL OF PHYSICS-CONDENSED MATTER 20 巻 ( 27 ) 2008年7月

Materials design and development of functional materials for industry 査読有り

Asahi Ryoji, Morikawa Takeshi, Hazama Hirofumi, Matsubara Masato

JOURNAL OF PHYSICS-CONDENSED MATTER 20 巻 ( 6 ) 頁： 064227 2008年2月

Nanostructural characterization of TiNiSn-based half-Heusler compounds 査読有り

Matsubara M., Asahi R., Nakagaki T., Isheim D., Seidman D. N.

PROCEEDINGS ICT 07: TWENTY-SIXTH INTERNATIONAL CONFERENCE ON THERMOELECTRICS 頁： 268 - 271 2008年

Nanostructural characterization of TiNiSn-based half-Heusler compounds 査読有り

Matsubara M.

International Conference on Thermoelectrics, ICT, Proceedings 頁： 263 - 266 2007年12月

Nitrogen complex species and its chemical nature in TiO2 for visible-light sensitized photocatalysis 査読有り

Asahi Ryoji, Morikawa Takeshi

CHEMICAL PHYSICS 339 巻 ( 1-3 ) 頁： 57 - 63 2007年10月

Crystallographic orientation analysis on calcium cobaltite ceramic grains textured by reactive-templated grain growth 査読有り

Tani T.

International Journal of Applied Ceramic Technology 4 巻 ( 4 ) 頁： 318 - 325 2007年8月

Properties of the gold oxides Au2O3 and Au2O: First-principles investigation 査読有り

Shi Hongqing, Asahi Ryoji, Stampfl Catherine

PHYSICAL REVIEW B 75 巻 ( 20 ) 2007年5月

Crystallographic orientation analysis on calcium cobaltite ceramic grains textured by reactive-templated grain growth 査読有り

Tani Toshihiko, Itahara Hiroshi, Kadoura Hiroaki, Asahi Ryoji

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY 4 巻 ( 4 ) 頁： 318 - 325 2007年

Mediated resonance effect of the vanadium 3d states on phase stability in the Al8V5 gamma-brass studied by first-principles FLAPW and LMTO-ASA electronic structure calculations 査読有り

Mizutani U., Asahi R., Sato H., Takeuchi T.

PHYSICAL REVIEW B 74 巻 ( 23 ) 2006年12月

Analysis of crystallographic orientation on textured ca-doped (ZnO) mIn2O3 ceramics by electron back scattering diffraction pattern 査読有り

Kaga Hisashi, Tani Toshihiko, Kadoura Hiroaki, Seki Juntaro, Asahi Ryoji

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 114 巻 ( 1335 ) 頁： 1022 - 1028 2006年11月

Extremely small thermal conductivity of the Al-based Mackay-type 1/1-cubic approximants 査読有り

Takeuchi Tsunehiro, Nagasako Naoyuki, Asahi Ryoji, Mizutani Uichiro

PHYSICAL REVIEW B 74 巻 ( 5 ) 2006年8月

First-principles calculations of Ag-Sb nanodot formation in thermoelectric AgPbmSbTe2+m (m=6,14,30) 査読有り

Hazama H, Mizutani U, Asahi R

PHYSICAL REVIEW B 73 巻 ( 11 ) 2006年3月

The Hume-Rothery electron concentration rule for a series of gamma-brasses studied by full-potential linearized augmented plane wave (FLAPW) band calculations 査読有り

Mizutani U, Asahi R, Sato H, Takeuchi T

PHILOSOPHICAL MAGAZINE 86 巻 ( 3-5 ) 頁： 645 - 654 2006年

Thermoelectric properties of Al-doped ZnO prepared by electrical field-assist sintering 査読有り

Kaga Hisashi, Asahi Ryoji

SCIENCE OF ENGINEERING CERAMICS III 317-318 巻頁： 811 - 814 2006年

High-temperature thermoelectric power generation module of layered oxides improved by multistage structure with Bi-Te module 査読有り

Asahi R.

International Conference on Thermoelectrics, ICT, Proceedings 2005 巻頁： 358 - 361 2005年12月

Interpretation of the Hume-Rothery electron concentration rule in the T2Zn11 (T=Ni, Pd, Co, and Fe) gamma brasses based on first-principles FLAPW calculations 査読有り

Asahi R, Sato H, Takeuchi T, Mizutani U

PHYSICAL REVIEW B 72 巻 ( 12 ) 2005年9月

Thermoelectric properties of Ca-doped (ZnO)<inf>m</inf>in<inf>2</inf>O <inf>3</inf> ceramics and their improvement upon texture 査読有り

Kaga H.

Ceramic Transactions 167 巻頁： 127 - 136 2005年8月

Verification of Hume-Rothery electron concentration rule in Cu5Zn8 and Cu9Al4 gamma brasses by ab initio FLAPW band calculations 査読有り

Asahi R, Sato H, Takeuchi T, Mizutani U

PHYSICAL REVIEW B 71 巻 ( 16 ) 2005年4月

Fully first-principles screened-exchange LDA calculations of excited states and optical properties of III-V semiconductors 査読有り

Rhim SH, Kim M, Freeman AJ, Asahi R

PHYSICAL REVIEW B 71 巻 ( 4 ) 2005年1月

High-temperature thermoelectric power generation module of layered oxides improved by multistage structure with Bi-Te module 査読有り

Asahi R, Tani T, Itahara H, Kaga H, Okuda K

ICT: 2005 24TH INTERNATIONAL CONFERENCE ON THERMOELECTRICS 頁： 358 - 361 2005年

Thermoelectric properties of Ca-doped (ZnO)(m)In2O3 ceramics and their improvement upon texture 査読有り

Kaga H, Asahi R, Tani T

DEVELOPMENTS IN DIELECTRIC MATERIALS AND ELECTRONIC DEVICES 167 巻頁： 127 - 136 2005年

Thermoelectric Properties of Highly Textured Ca-Doped (ZnO)_mIn_2O_3 Ceramics 査読有り

Kaga Hisashi, Asahi Ryoji, Tani Toshihiko

Japanese journal of applied physics. Pt. 1, Regular papers & short notes 43 巻 ( 10 ) 頁： 7133 - 7136 2004年10月

Thermoelectric Properties of Doped (ZnO)_mIn_2O_3 査読有り

Kaga Hisashi, Asahi Ryoji, Tani Toshihiko

Japanese journal of applied physics. Pt. 1, Regular papers & short notes 43 巻 ( 6 ) 頁： 3540 - 3543 2004年6月

First Principles Calculations of Auger Recombination and Impact Ionization Rates in Semiconductors 査読有り

Picozzi S., Asahi R., Freeman A. J.

JOURNAL OF COMPUTATIONAL ELECTRONICS 2 巻 ( 2-4 ) 頁： 197 - 202 2003年12月

Growth of In2O3(ZnO)(5) platelet micro-crystals by flux methods 査読有り

Xia CT, Asahi R, Tani T

JOURNAL OF CRYSTAL GROWTH 254 巻 ( 1-2 ) 頁： 144 - 150 2003年6月

窒素ドープ型酸化チタン可視光応答光触媒の解析査読有り

大脇健史, 森川健志, 青木恒勇, 旭良司, 多賀康訓, 磯村典武

表面科学 : hyomen kagaku = Journal of the Surface Science Society of Japan 24 巻 ( 1 ) 頁： 25 - 30 2003年1月

記述言語：日本語掲載種別：研究論文（その他学術会議資料等）出版者・発行元：公益社団法人日本表面科学会

N-doped titanium oxide photocatalyst is found to be activated by visible light irradiation as well as ultraviolet irradiation. We evaluated its crystal structure, N states in the lattice, composition, and surface morphology using X-ray diffiraction (XRD), X-ray photoemission spectroscopy (XPS), and scanning probe microscopy (SPM). As a result, it is found that the materials have rutile or anatase crystal structure with nitrogen doped into substitutional sites of oxygen in TiO2, which contributes band gap narrowing. It is also confirmed that XPS measurement was influenced by surface treatment such as Ar ion bombardment.

DOI： 10.1380/jsssj.24.25

Accurate first-principles detailed-balance determination of Auger recombination and impact ionization rates in semiconductors 査読有り

Picozzi S, Asahi R, Geller CB, Freeman AJ

PHYSICAL REVIEW LETTERS 89 巻 ( 19 ) 2002年11月

Impact Ionization in GaAs within A Screened Exchange Density Functional Formalism 査読有り

Picozzi S.

Journal of Computational Electronics 1 巻 ( 3 ) 頁： 421 - 424 2002年10月

First-principles calculations for understanding high conductivity and optical transparency in InxCd1-x films 査読有り

Asahi R, Wang A, Babcock JR, Edleman NL, Metz AW, Lane MA, Dravid VP, Kannewurf CR, Freeman AJ, Marks TJ

THIN SOLID FILMS 411 巻 ( 1 ) 頁： 101 - 105 2002年5月

Surface properties of the refractory metal-nitride semiconductor ScN: Screened-exchange LDA-FLAPW investigations 査読有り

Stampfl C, Asahi R, Freeman AJ

PHYSICAL REVIEW B 65 巻 ( 16 ) 頁： 1 - 4 2002年4月

Impact ionization in GaAs: A screened exchange density-functional approach 査読有り

Picozzi S, Asahi R, Geller CB, Continenza A, Freeman AJ

PHYSICAL REVIEW B 65 巻 ( 11 ) 頁： 1 - 4 2002年3月

Photocatalysts sensitive to visible light - Response 査読有り

Asahi R, Morikawa T, Ohwaki T, Aoki K, Taga Y

SCIENCE 295 巻 ( 5555 ) 頁： 627 - 627 2002年1月

Electronic structure of misfit-layered calcium cobaltite 査読有り

Asahi R, Sugiyama J, Tani T, Xia CT

XXI INTERNATIONAL CONFERENCE ON THERMOELECTRICS, PROCEEDINGS ICT '02 頁： 203 - 206 2002年

Excited states and optical properties entirely from first principles: Extended FLAPW method and its graphical user interface 査読有り

Kim MY, Asahi R, Freeman AJ

JOURNAL OF COMPUTER-AIDED MATERIALS DESIGN 9 巻 ( 3 ) 頁： 173 - 201 2002年

Electronic structure of misfit-layered calcium cobaltite 査読有り

Asahi R., Sugiyama J., Tani T.

Physical Review B - Condensed Matter and Materials Physics 66 巻 ( 15 ) 頁： 1 - 7 2002年

Electronic structure of misfit-layered calcium cobaltite 査読有り

Asahi R.

International Conference on Thermoelectrics, ICT, Proceedings 2002-January 巻頁： 203 - 206 2002年

Effect of GGA on the half-metallicity of the itinerant ferromagnet CoS2 査読有り

Shishidou T, Freeman AJ, Asahi R

PHYSICAL REVIEW B 64 巻 ( 18 ) 2001年11月

Electronic structure and small polaron hole transport of copper aluminate 査読有り

Ingram BJ, Mason TO, Asahi R, Park KT, Freeman AJ

PHYSICAL REVIEW B 64 巻 ( 15 ) 2001年10月

Computational band-structure engineering of III-V semiconductor alloys 査読有り

Geller CB, Wolf W, Picozzi S, Continenza A, Asahi R, Mannstadt W, Freeman AJ, Wimmer E

APPLIED PHYSICS LETTERS 79 巻 ( 3 ) 頁： 368 - 370 2001年7月

Visible-light photocatalysis in nitrogen-doped titanium oxides 査読有り

Asahi R, Morikawa T, Ohwaki T, Aoki K, Taga Y

SCIENCE 293 巻 ( 5528 ) 頁： 269 - 271 2001年7月

Indium-cadmium-oxide films having exceptional electrical conductivity and optical transparency: Clues for optimizing transparent conductors 査読有り

Wang A, Babcock JR, Edleman NL, Metz AW, Lane MA, Asahi R, Dravid VP, Kannewurf CR, Freeman AJ, Marks TJ

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 98 巻 ( 13 ) 頁： 7113 - 7116 2001年6月

Band-Gap Narrowing of Titanium Dioxide by Nitrogen Doping 査読有り

Morikawa Takeshi, Asahi Ryoji, Ohwaki Takeshi, AOKI Koyu, TAGA Yasunori

Japanese journal of applied physics. Pt. 2, Letters 40 巻 ( 6 ) 頁： L561 - L563 2001年6月

Electronic structure and physical properties of early transition metal mononitrides: Density-functional theory LDA, GGA, and screened-exchange LDA FLAPW calculations 査読有り

Stampfl C, Mannstadt W, Asahi R, Freeman AJ

PHYSICAL REVIEW B 63 巻 ( 15 ) 2001年4月

Band-Gap Narrowing of Titanium Dioxide by Nitrogen Doping. 査読有り

Morikawa Takeshi, Asahi Ryoji, Ohwaki Takeshi, Aoki Koyu, Taga Yasunori

Japanese Journal of Applied Physics 40 巻 ( 6 ) 頁： L561 - L563 2001年

記述言語：英語掲載種別：研究論文（その他学術会議資料等）出版者・発行元：The Japan Society of Applied Physics

TiO2-based powder, including 0.1 at% of N doped in the rutile lattice, has been synthesized by oxidation of TiN. As a result, a significant shift of the absorption edge to a lower energy in the visible-light region has been observed. The substitutional doping of N into the TiO2 lattice is found to be effective; its 2p states contribute to the band-gap narrowing by mixing with O 2p as shown in ab initio electronic structure calculations.

DOI： 10.1143/JJAP.40.L561

Effect of GGA on the half-metallicity of the itinerant ferromagnet CoS2 査読有り

Shishidou T., Freeman, A.J., Asahi, R.

Physical Review B - Condensed Matter and Materials Physics 64 巻 ( 18 ) 2001年

Screened-exchange LDA methods for films and superlattices with applications to the Si(100)2X1 surface and InAs/InSb superlattices 査読有り

Asahi R, Mannstadt W, Freeman AJ

PHYSICAL REVIEW B 62 巻 ( 4 ) 頁： 2552 - 2561 2000年7月

Electronic and optical properties of anatase TiO2 査読有り

Asahi R, Taga Y, Mannstadt W, Freeman AJ

PHYSICAL REVIEW B 61 巻 ( 11 ) 頁： 7459 - 7465 2000年3月

Volume and composition dependence of direct and indirect band gaps in ordered ternary III-V semiconductor compounds: A screened-exchange LDA study 査読有り

Picozzi S, Continenza A, Asahi R, Mannstadt W, Freeman AJ, Wolf W, Wimmer E, Geller CB

PHYSICAL REVIEW B 61 巻 ( 7 ) 頁： 4677 - 4684 2000年2月

Moss-Burstein and plasma reflection characteristics of heavily doped n-type InxGa1-xAs and InPyAs1-y 査読有り

Charache GW, DePoy DM, Raynolds JE, Baldasaro PF, Miyano KE, Holden T, Pollak FH, Sharps PR, Timmons ML, Geller CB, Mannstadt W, Asahi R, Freeman AJ, Wolf W

JOURNAL OF APPLIED PHYSICS 86 巻 ( 1 ) 頁： 452 - 458 1999年7月

Optical properties and electronic structures of semiconductors with screened-exchange LDA 査読有り

Asahi R, Mannstadt W, Freeman AJ

PHYSICAL REVIEW B 59 巻 ( 11 ) 頁： 7486 - 7492 1999年3月

Micromachined sensors using polysilicon sacrificial layer etching technology 査読有り

Tabata O, Shimaoka K, Asahi R, Sugiyama S

SENSORS AND MATERIALS 8 巻 ( 1 ) 頁： 57 - 67 1996年

MICROMACHINED SENSORS USING POLYSILICON SACRIFICIAL LAYER ETCHING TECHNOLOGY 査読有り

SUGIYAMA S, TABATA O, SHIMAOKA K, ASAHI R

INTERNATIONAL ELECTRON DEVICES MEETING 1994 - IEDM TECHNICAL DIGEST 頁： 127 - 130 1994年

ANISOTROPIC ETCHING OF SILICON IN TMAH SOLUTIONS 査読有り

TABATA O, ASAHI R, FUNABASHI H, SHIMAOKA K, SUGIYAMA S

SENSORS AND ACTUATORS A-PHYSICAL 34 巻 ( 1 ) 頁： 51 - 57 1992年7月

INTEGRATED PYROELECTRIC INFRARED-SENSOR USING PVDF THIN-FILM DEPOSITED BY ELECTRO-SPRAY METHOD 査読有り

ASAHI R, SAKATA J, TABATA O, MOCHIZUKI M, SUGIYAMA S, TAGA Y

FERROELECTRIC THIN FILMS III 310 巻頁： 79 - 84 1992年

INFRARED LINEAR IMAGE SENSOR USING A POLY-SI PN JUNCTION DIODE-ARRAY 査読有り

TANAKA A, SUZUKI M, ASAHI R, TABATA O, SUGIYAMA S

INFRARED PHYSICS 33 巻 ( 4 ) 頁： 229 - 236 1992年

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