Faculty Profiles - ASAHI Ryoji

Papers - ASAHI Ryoji

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Dielectric tensor of perovskite oxides at finite temperature using equivariant graph neural network potentials Reviewed Open Access

Alex Kutana, Koki Yoshimochi, Ryoji Asahi

Science and Technology of Advanced Materials: Methods Vol. 5 page： 2497254 2025.6

Representing Born effective charges with equivariant graph convolutional neural networks. Reviewed Open Access

Scientific reports Vol. 15 ( 1 ) page： 16719 2025.5

Enhancing fluoride-ion conduction via doping-induced anionic ordering in an n = 1 Ba-based Ruddlesden-Popper oxyfluoride structure Reviewed Open Access

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

Solid State Ionics Vol. 424 page： 116866 2025.4

Polyvalent machine-learned potential for cobalt: From bulk to nanoparticles Reviewed International coauthorship

Marthe Bideault, Jérôme Creuze, Ryoji Asahi, Erich Wimmer

Physical Review Materials Vol. 8 page： 123803 2024.12

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

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 page： 2404030 2024.12

Roadmap on methods and software for electronic structure based simulations in chemistry and materials Invited Reviewed International coauthorship

Volker Blum, Ryoji Asahi et al.

Electronic Structure Vol. 6 ( 4 ) page： 042501 2024.11

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

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

Chemistry of Materials Vol. 36 ( 11 ) page： 5671 - 5677 2024.5

Machine learning and atomistic origin of high dielectric permittivity in oxides. Reviewed

Shimano Y, Kutana A, Asahi R

Scientific reports Vol. 13 ( 1 ) page： 22236 2023.12

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (other academic) Publisher：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 Invited Reviewed International coauthorship

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

JOURNAL OF MATERIALS RESEARCH ( 38 ) page： 5151 - 5160 2023.9

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (other academic) Publisher：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 Reviewed

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

ACS Omega Vol. 8 ( 24 ) page： 220003 - 22017 2023.6

Automatic knowledge acquisition from superconductivity information in literature Reviewed

Kento Mitsui, Yutaka Sasaki, Ryoji Asahi

Science and Technology of Advanced Materials: Methods Vol. 3 page： 2206532 2023.5

Challenges for fluoride superionic conductors: fundamentals, design, and applications Invited Reviewed

Tsuyoshi Takami, Chanachai Pattanathummasid, Alex Kutana, Ryoji Asahi

Journal of Physics: Condensed Matter Vol. 35 page： 293002 2023.4

Permittivity boosting by induced strain from local doping in titanates from first principles Reviewed

A. Kutana, Y. Shimano, R. Asahi

Scientific Reports Vol. 13 page： 3761 2023.3

Ultrafast charge-transfer dynamics in a visible-light-excited iridium(III) terpyridine 2-phenylpyridine complex studied by femtosecond X-ray absorption spectroscopy Reviewed International coauthorship

K. Yamanaka, T. Morikawa, R. Asahi

JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY Vol. 435 page： 114267 2023.2

Superconductivity information extraction from the literature: A new corpus and its evaluations Reviewed

Kyosuke Yamaguchi, Ryoji Asahi, Yutaka Sasaki

Advanced Engineering Informatics Vol. 54 page： 101768 2022.10

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

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

ACTA MATERIALIA Vol. 236 2022.9

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 Reviewed

Lee J., Asahi R.

Journal of Physical Chemistry C Vol. 126 ( 32 ) page： 13548 - 13559 2022.8

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

INORGANIC CHEMISTRY Vol. 60 ( 14 ) page： 10371 - 10379 2021.7

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (other academic) Publisher：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 Reviewed

Lee Joohwi, Asahi Ryoji

COMPUTATIONAL MATERIALS SCIENCE Vol. 190 2021.4

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

Miwa Kazutoshi, Asahi Ryoji

Solid State Ionics Vol. 361 2021.3

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

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

JOURNAL OF THE EUROPEAN CERAMIC SOCIETY Vol. 41 ( 2 ) page： 1352 - 1359 2021.2

Stationary interatomic force constant matrix method with ultrasoft pseudopotentials Reviewed

Miwa Kazutoshi, Asahi Ryoji

PHYSICAL REVIEW B Vol. 102 ( 17 ) 2020.11

On-the-Fly Active Learning of Interatomic Potentials for Large-Scale Atomistic Simulations Reviewed

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

JOURNAL OF PHYSICAL CHEMISTRY LETTERS Vol. 11 ( 17 ) page： 6946 - 6955 2020.9

Charge Trapping Process in Photoexcited Nitrogen-Doped Titanium Oxides Reviewed

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 Vol. 59 ( 15 ) page： 10439 - 10449 2020.8

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

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

JOURNAL OF CHEMICAL PHYSICS Vol. 152 ( 23 ) page： 234102 2020.6

Discovery of superionic conductors by ensemble-scope descriptor Reviewed

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

NPG ASIA MATERIALS Vol. 12 ( 1 ) 2020.4

Design Rules for High Oxygen-Ion Conductivity in Garnet-Type Oxides Reviewed

Lee Joohwi, Ohba Nobuko, Asahi Ryoji

CHEMISTRY OF MATERIALS Vol. 32 ( 4 ) page： 1358 - 1370 2020.2

Identifying superionic conductors by materials informatics and high-throughput synthesis Reviewed

Matsubara Masato, Suzumura Akitoshi, Ohba Nobuko, Asahi Ryoji

COMMUNICATIONS MATERIALS Vol. 1 ( 1 ) 2020.2

SC-CoMIcs: A superconductivity corpus for materials informatics Reviewed

Yamaguchi K., Asahi R., Sasaki Y.

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

Atomistic Modeling of Photoelectric Cells for Artificial Photosynthesis Reviewed

Asahi Ryoji, Jinnouchi Ryosuke

MULTISCALE SIMULATIONS FOR ELECTROCHEMICAL DEVICES page： 107 - 145 2020

Multiscale Simulations for Electrochemical Devices Preface Reviewed

Asahi Ryoji

MULTISCALE SIMULATIONS FOR ELECTROCHEMICAL DEVICES page： XI - XIV 2020

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

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

SCIENTIFIC REPORTS Vol. 9 ( 1 ) page： 15123 2019.10

y Path integral study on C15-type Laves TiCr2 hydride Reviewed

Miwa Kazutoshi, Asahi Ryoji

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY Vol. 44 ( 42 ) page： 23708 - 23715 2019.9

Phosphorescent Material Search Using a Combination of High-Throughput Evaluation and Machine Learning Reviewed

Hazama Hirofumi, Sobue Susumu, Tajima Shin, Asahi Ryoji

INORGANIC CHEMISTRY Vol. 58 ( 16 ) page： 10936 - 10943 2019.8

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

Matsubara Masato, Suzumura Akitoshi, Tajima Shin, Asahi Ryoji

ACS COMBINATORIAL SCIENCE Vol. 21 ( 5 ) page： 400 - 407 2019.5

Water Facilitated Electrochemical Reduction of CO2 on Cobalt-Porphyrin Catalysts Reviewed

Miyamoto Kaito, Asahi Ryoji

JOURNAL OF PHYSICAL CHEMISTRY C Vol. 123 ( 15 ) page： 9944 - 9948 2019.4

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

Ohba Nobuko, Ogata Shuji, Asahi Ryoji

JOURNAL OF PHYSICAL CHEMISTRY C Vol. 123 ( 15 ) page： 9673 - 9679 2019.4

Collaborative effects of Zn and Sb Co-doping in magnesium silicide for thermoelectric applications Reviewed

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

JOURNAL OF ALLOYS AND COMPOUNDS Vol. 781 page： 606 - 612 2019.4

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

Lee Joohwi, Ohba Nobuko, Asahi Ryoji

SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS Vol. 20 ( 1 ) page： 144 - 159 2019.3

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

Nagasako Naoyuki, Suzumura Akitoshi, Asahi Ryoji

ACTA MATERIALIA Vol. 166 page： 37 - 46 2019.3

Oxygen conduction mechanism in Ca3Fe2Ge3O12 garnet-type oxide Reviewed

Lee Joohwi, Ohba Nobuko, Asahi Ryoji

SCIENTIFIC REPORTS Vol. 9 ( 1 ) page： 2593 2019.2

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

Matsubara M., Masuoka Y., Asahi R.

JOURNAL OF ALLOYS AND COMPOUNDS Vol. 774 page： 731 - 738 2019.2

Solar Thermal Cogeneration System Using a Cylindrical Thermoelectric Module Reviewed

Suzumura Akitoshi, Hazama Hirofumi, Matsubara Masato, Asahi Ryoji

JOURNAL OF ELECTRONIC MATERIALS Vol. 48 ( 1 ) page： 467 - 474 2019.1

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

Miwa Kazutoshi, Asahi Ryoji

PHYSICAL REVIEW MATERIALS Vol. 2 ( 10 ) 2018.10

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

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

PHYSICAL CHEMISTRY CHEMICAL PHYSICS Vol. 20 ( 39 ) page： 25275 - 25294 2018.10

Cylindrical thermoelectric generator with water heating system for high solar energy conversion efficiency Reviewed

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

APPLIED ENERGY Vol. 226 page： 381 - 388 2018.9

Phase-field modeling of stress generation in polycrystalline LiCoO2 Reviewed

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

SOLID STATE IONICS Vol. 319 page： 209 - 217 2018.6

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

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

PHYSICAL CHEMISTRY CHEMICAL PHYSICS Vol. 20 ( 16 ) page： 11342 - 11346 2018.4

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

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

JOURNAL OF PHYSICAL CHEMISTRY C Vol. 122 ( 4 ) page： 1921 - 1929 2018.2

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

Lee Joohwi, Ohba Nobuko, Asahi Ryoji

RSC ADVANCES Vol. 8 ( 45 ) page： 25534 - 25545 2018

Linear independent non-negative matrix factorization for automatic decomposition of experimental spectra Reviewed

KIKKAWA Nobuaki, SUZUMURA Akitoshi, TAJIMA Shin, YAMAKAWA Shunsuke, ASAHI Ryoji

Proceedings of the Annual Conference of JSAI Vol. 2018 ( 0 ) page： 3Z101 - 3Z101 2018

A universal 3D voxel descriptor for solid-state materials informatics with convolutional neural networks Reviewed

KAJITA Seiji, OHBA Nobuko, ASAHI Ryoji

Proceedings of the Annual Conference of JSAI Vol. 2018 ( 0 ) page： 3Z102 - 3Z102 2018

Authorship：Last author Language：Japanese Publishing type：Research paper (other academic) Publisher：The Japanese Society for Artificial Intelligence

Materials informatics (MI) is a promising approach to liberate us from the time-consuming trial and error process for material discoveries. Contrary to molecular systems, however, practical successes of the solid-state MI are very scarce because existing descriptors insufficiently describe 3D features of eld quantities (e.g., electron distributions and local potentials). We develop a simple, generic 3D voxel descriptor that compacts any field quantities, in such a suitable way to implement convolutional neural networks. We examine the reciprocal-lattice 3D voxel space descriptor encoded from the electron distribution by a regression task with 680 oxides data. The present scheme outperforms other descriptors in the prediction of Hartree energies that are signicantly relevant to the long-wavelength distribution of the valence electrons.

DOI： 10.11517/pjsai.JSAI2018.0_3Z102

Visualization of SEM/EBSD Features of Ionic Conductivity with Convolutional Neural Networks Reviewed

KONDO Ruho, YAMAKAWA Shunsuke, MASUOKA Yumi, TAJIMA Shin, ASAHI Ryoji

Proceedings of the Annual Conference of JSAI Vol. 2018 ( 0 ) page： 3Z103 - 3Z103 2018

Authorship：Last author Language：Japanese Publishing type：Research paper (other academic) Publisher：The Japanese Society for Artificial Intelligence

To automatically extract the features required to predict the material properties from microstructure, we utilized convolutional newral networks (CNNs). Training of CNNs was carried out by using experimentally obtained scanning electron microscope images and ionic conductivities. After training, the nodes, which placed after global average pooling (GAP), specically activated by passing through the images with high/low ionic conductivities were searched. Then, the corresponding feature maps just before GAP operations were shown. We found that the CNNs focused on the reagion containing large voids and on the area without any crystal defects for the specic features for the material with high ionic conductivities while on the small voids for low ionic conductivities. Such observations agree with knowledge of materials engineering.

DOI： 10.11517/pjsai.JSAI2018.0_3Z103

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

Kajita Seiji, Ohba Nobuko, Jinnouchi Ryosuke, Asahi Ryoji

SCIENTIFIC REPORTS Vol. 7 ( 1 ) page： 16991 2017.12

Improvement of power factor of n-type Bi2Te3 by dispersed nanosized Ga2Te3 precipitates Reviewed

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

JOURNAL OF ALLOYS AND COMPOUNDS Vol. 726 page： 578 - 586 2017.12

Microstructure recognition using convolutional neural networks for prediction of ionic conductivity in ceramics Reviewed

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

ACTA MATERIALIA Vol. 141 page： 29 - 38 2017.12

Extrapolating Energetics on Clusters and Single-Crystal Surfaces to Nanoparticles by Machine-Learning Scheme Reviewed

Jinnouchi Ryosuke, Hirata Hirohito, Asahi Ryoji

JOURNAL OF PHYSICAL CHEMISTRY C Vol. 121 ( 47 ) page： 26397 - 26405 2017.11

Study of the conformation of polyelectrolyte aggregates using coarse-grained molecular dynamics simulations Reviewed

Mima Toshiki, Kinjo Tomoyuki, Yamakawa Shunsuke, Asahi Ryoji

SOFT MATTER Vol. 13 ( 35 ) page： 5991 - 5999 2017.9

Predicting Catalytic Activity of Nanoparticles by a DFT-Aided Machine-Learning Algorithm Reviewed

Jinnouchi Ryosuke, Asahi Ryoji

JOURNAL OF PHYSICAL CHEMISTRY LETTERS Vol. 8 ( 17 ) page： 4279 - 4283 2017.9

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

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

MATERIALS RESEARCH EXPRESS Vol. 4 ( 4 ) 2017.4

Prediction of Ionic Conductivity from Ceramics Microstructure via Convolutional Neural Networks

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

The Proceedings of The Computational Mechanics Conference Vol. 2017 ( 0 ) 2017

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

Matsubara M., Asahi R.

JOURNAL OF ELECTRONIC MATERIALS Vol. 45 ( 3 ) page： 1669 - 1678 2016.3

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

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

ACTA MATERIALIA Vol. 105 page： 347 - 354 2016.2

Transport properties of the Cu2ZnSnS4 bulk systems: Effects of nonstoichiometry and defect formation Reviewed

Hazama Hirofumi, Tajima Shin, Masuoka Yumi, Asahi Ryoji

JOURNAL OF ALLOYS AND COMPOUNDS Vol. 657 page： 179 - 183 2016.2

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

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

JOURNAL OF PHYSICAL CHEMISTRY C Vol. 119 ( 48 ) page： 26925 - 26936 2015.12

Sodium distribution in solar-grade Cu2ZnSnS4 layers using atom-probe tomographic technique Reviewed

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 54 ( 11 ) 2015.11

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

Ohba Nobuko, Ogata Shuji, Kouno Takahisa, Asahi Ryoji

COMPUTATIONAL MATERIALS SCIENCE Vol. 108 page： 250 - 257 2015.10

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

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

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Vol. 137 ( 35 ) page： 11517 - 11525 2015.9

Improvement of the open-circuit voltage of Cu2ZnSnS4 solar cells using a two-layer structure Reviewed

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

APPLIED PHYSICS EXPRESS Vol. 8 ( 8 ) 2015.8

Theoretical Insights into the Impact of Ru Catalyst Anchors on the Efficiency of Photocatalytic CO2 Reduction on Ta2O5 Reviewed

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

JOURNAL OF PHYSICAL CHEMISTRY B Vol. 119 ( 24 ) page： 7186 - 7197 2015.6

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

Tetsuka H., Nagoya A., Asahi R.

JOURNAL OF MATERIALS CHEMISTRY C Vol. 3 ( 15 ) page： 3536 - 3541 2015

Presence of a Doubly-Splitting Site and Its Effect on Thermoelectric Properties of Cu4SnS4 Reviewed

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

MATERIALS TRANSACTIONS Vol. 56 ( 6 ) page： 858 - 863 2015

Language：English Publishing type：Research paper (other academic) Publisher：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

Web of Science

Scopus

059 Phase-field modeling of stress generation in a delithiated positive electrode

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

The Proceedings of The Computational Mechanics Conference Vol. 2015 ( 0 ) page： _059 - 1_-_059-2_ 2015

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

Asahi Ryoji, Morikawa Takeshi, Irie Hiroshi, Ohwaki Takeshi

CHEMICAL REVIEWS Vol. 114 ( 19 ) page： 9824 - 9852 2014.10

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

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

MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING Vol. 22 ( 7 ) 2014.10

Atom-probe tomographic study of interfaces of Cu2ZnSnS4 photovoltaic cells Reviewed

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

APPLIED PHYSICS LETTERS Vol. 105 ( 9 ) 2014.9

Effect of microstructure on discharge properties of polycrystalline LiCoO2 Reviewed

Yamakawa Shunsuke, Yamasaki Hisatsugu, Koyama Toshiyuki, Asahi Ryoji

SOLID STATE IONICS Vol. 262 page： 56 - 60 2014.9

Improvement in Thermoelectric Properties of Se-Free Cu3SbS4 Compound Reviewed

Suzumura Akitoshi, Watanabe Masaki, Nagasako Naoyuki, Asahi Ryoji

JOURNAL OF ELECTRONIC MATERIALS Vol. 43 ( 6 ) page： 2356 - 2361 2014.6

Surface segregations in platinum-based alloy nanoparticles Reviewed

Yamakawa Shunsuke, Asahi Ryoji, Koyama Toshiyuki

SURFACE SCIENCE Vol. 622 page： 65 - 70 2014.4

A metathesis reaction route to obtain fine Mg2Si particles Reviewed

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

CHEMICAL COMMUNICATIONS Vol. 50 ( 33 ) page： 4315 - 4318 2014

Improvement of the open-circuit voltage of CU2ZnSnS4 cells using a two-layered process Reviewed

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

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

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

Munekata Toshihisa, Suzuki Takahisa, Yamakawa Shunsuke, Asahi Ryoji

PHYSICAL REVIEW E Vol. 88 ( 5 ) page： 052314 2013.11

Phase-Field Modeling of Phase Transformations in Platinum-Based Alloy Nanoparticles Reviewed

Yamakawa Shunsuke, Asahi Ryoji, Koyama Toshiyuki

MATERIALS TRANSACTIONS Vol. 54 ( 8 ) page： 1242 - 1249 2013.8

Language：English Publishing type：Research paper (other academic) Publisher：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

Web of Science

Scopus

Numerical study of Li diffusion in polycrystalline LiCoO2 Reviewed

Yamakawa Shunsuke, Yamasaki Hisatsugu, Koyama Toshiyuki, Asahi Ryoji

JOURNAL OF POWER SOURCES Vol. 223 page： 199 - 205 2013.2

1611 Effect of Microstructure on Li Diffusivity of Polycrystalline LiCoC_2

Yamakawa Shunsuke, Yamasaki Hisatsugu, Ide Kazuto, Asahi Ryoji, Koyama Toshiyuki

The Proceedings of The Computational Mechanics Conference Vol. 2013 ( 0 ) page： _1611 - 1_-_1611-2_ 2013

2415 A hybrid quantum-classical simulation study on the interaction effects between Li-ions for those diffusion in graphite

OHBA Nobuko, OGATA Shuji, KOUNO Takahisa, KOBAYASHI Ryo, TAMURA Tomoyuki, ASAHI Ryoji

The Proceedings of The Computational Mechanics Conference Vol. 2013 ( 0 ) page： _2415 - 1_-_2415-2_ 2013

Model GW study of the late transition metal monoxides Reviewed

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

JOURNAL OF CHEMICAL PHYSICS Vol. 137 ( 15 ) page： 154110 2012.10

Optically Tunable Amino-Functionalized Graphene Quantum Dots Reviewed

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

ADVANCED MATERIALS Vol. 24 ( 39 ) page： 5333 - 5338 2012.10

Thermoelectric Properties of Off-Stoichiometric Ti-Ni-Sn Half-Heusler Systems Reviewed

Hazama Hirofumi, Matsubara Masato, Asahi Ryoji

JOURNAL OF ELECTRONIC MATERIALS Vol. 41 ( 6 ) page： 1730 - 1734 2012.6

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

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

Journal of the Physical Society of Japan Vol. 81 ( 2 ) page： 23601 - 23601 2012.2

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

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

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 81 ( 2 ) 2012.2

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

Nagasako Naoyuki, Asahi Ryoji, Hafner Juergen

PHYSICAL REVIEW B Vol. 85 ( 2 ) 2012.1

1111 Phase-Field Study of Compositional Variation within Bimetallic Nanoparticle

Yamakawa Shunsuke, Sakurai Shogo, Asahi Ryoji, Koyama Toshiyuki

The Proceedings of The Computational Mechanics Conference Vol. 2012 ( 0 ) page： 68 - 69 2012

2110 Hybrid quantum-classical simulation with DC-RGDFT on thermal diffusion of Li in Graphite

OHBA Nobuko, OGATA Shuji, KOUNO Takahisa, KOBAYASHI Ryo, TAMURA Tomoyuki, ASAHI Ryoji

The Proceedings of The Computational Mechanics Conference Vol. 2012 ( 0 ) page： 191 - 192 2012

First-principles study of Cu2ZnSnS4 and the related band offsets for photovoltaic applications Reviewed

Nagoya A., Asahi R., Kresse G.

JOURNAL OF PHYSICS-CONDENSED MATTER Vol. 23 ( 40 ) 2011.10

A hybrid quantum-classical simulation study on stress-dependence of li diffusivity in graphite Reviewed

Ohba N.

CMES - Computer Modeling in Engineering and Sciences Vol. 75 ( 3-4 ) page： 247 - 264 2011.9

Improvement of thermoelectric properties for half-Heusler TiNiSn by interstitial Ni defects Reviewed

Hazama Hirofumi, Matsubara Masato, Asahi Ryoji, Takeuchi Tsunehiro

JOURNAL OF APPLIED PHYSICS Vol. 110 ( 6 ) 2011.9

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

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

PHYSICAL REVIEW B Vol. 84 ( 5 ) 2011.8

Computational Materials Design for High-performance Thermoelectrics Reviewed

ASAHI Ryoji, HAZAMA Hirofumi, NAGASAKO Naoyuki, MATSUBARA Masato

Ceramics Japan Vol. 46 ( 6 ) page： 505 - 509 2011.6

Fabrication of Nanocomposite Thermoelectric Materials by a Pulsed Laser Deposition Method Reviewed

Matsubara Masato, Azuma Hirozumi, Asahi Ryoji

JOURNAL OF ELECTRONIC MATERIALS Vol. 40 ( 5 ) page： 1176 - 1180 2011.5

Thermoelectric Properties of Si2Ti-Type Al-(Mn,Cr,Fe)-Si Alloys Reviewed

Toyama Yasuhiro, Hazama Hirofumi, Asahi Ryoji, Takeuchi Tsunehiro

JOURNAL OF ELECTRONIC MATERIALS Vol. 40 ( 5 ) page： 1052 - 1056 2011.5

A Hybrid Quantum-Classical Simulation Study on Stress-Dependence of Li Diffusivity in Graphite Reviewed

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

CMES-COMPUTER MODELING IN ENGINEERING & SCIENCES Vol. 75 ( 3-4 ) page： 247 - 265 2011.5

1506 Hybrid quantum-classical simulation : development of O(N)-real-space DFT method and application to the Li-graphite intercalation compound

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

The Proceedings of The Computational Mechanics Conference Vol. 2011 ( 0 ) page： 481 - 482 2011

906 Phase-field Modeling of Lithium Intercalation in Polycrystalline Oxide

Yamakawa Shunsuke, Yamasaki Hisatsugu, Koyama Toshiyuki, Asahi Ryoji

The Proceedings of The Computational Mechanics Conference Vol. 2011 ( 0 ) page： 296 - 297 2011

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

Tanaka Isao, Hafner Juergen, Wimmer Erich, Asahi Ryoji

JOURNAL OF PHYSICS-CONDENSED MATTER Vol. 22 ( 38 ) page： 380301 2010.9

Electronic Structure and Thermoelectric Properties of Al-Mn-Fe-Si Alloys Reviewed

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

JOURNAL OF ELECTRONIC MATERIALS Vol. 39 ( 9 ) page： 1433 - 1438 2010.9

Electronic Structure and Thermoelectric Properties of Si_2Ti-Type Al-(Mn, X)-Si (X=Cr, Fe) Alloys Reviewed

TOYAMA Yasuhiro, HAZAMA Hirofumi, ASAHI Ryoji, TAKEUCHI Tsunehiro

Journal of the Japan Institute of Metals and Materials Vol. 74 ( 9 ) page： 605 - 609 2010.9

Language：English Publishing type：Research paper (other academic) Publisher：The Japan Institute of Metals and Materials

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 Reviewed

Toyama Yasuhiro, Hazama Hirofumi, Asahi Ryoji, Takeuchi Tsunehiro

JOURNAL OF THE JAPAN INSTITUTE OF METALS Vol. 74 ( 9 ) page： 605 - 609 2010.9

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

Hazama Hirofumi, Asahi Ryoji, Matsubara Masato, Takeuchi Tsunehiro

JOURNAL OF ELECTRONIC MATERIALS Vol. 39 ( 9 ) page： 1549 - 1553 2010.9

Thermoelectric Properties of Si2Ti-Type Al-Mn-Si Alloys Reviewed

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

MATERIALS TRANSACTIONS Vol. 51 ( 6 ) page： 1127 - 1135 2010.6

Language：English Publishing type：Research paper (other academic) Publisher：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

Web of Science

Scopus

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

Nagasako Naoyuki, Jahnatek Michal, Asahi Ryoji, Hafner Juergen

PHYSICAL REVIEW B Vol. 81 ( 9 ) 2010.3

Defect formation and phase stability of Cu2ZnSnS4 photovoltaic material Reviewed

Nagoya Akihiro, Asahi Ryoji, Wahl Roman, Kresse Georg

PHYSICAL REVIEW B Vol. 81 ( 11 ) 2010.3

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

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

APPLIED PHYSICS LETTERS Vol. 95 ( 11 ) 2009.9

Preparation of Conducting Polyaniline-Bismuth Nanoparticle Composites by Planetary Ball Milling Reviewed

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

JOURNAL OF ELECTRONIC MATERIALS Vol. 38 ( 7 ) page： 1443 - 1449 2009.7

Thermoelectric Properties of Organic Charge-Transfer Compounds Reviewed

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

JOURNAL OF ELECTRONIC MATERIALS Vol. 38 ( 7 ) page： 1171 - 1175 2009.7

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

Paier Joachim, Asahi Ryoji, Nagoya Akihiro, Kresse Georg

PHYSICAL REVIEW B Vol. 79 ( 11 ) 2009.3

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 Reviewed

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

ZEITSCHRIFT FUR KRISTALLOGRAPHIE Vol. 224 ( 1-2 ) page： 17 - 20 2009

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

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

JOURNAL OF PHYSICS-CONDENSED MATTER Vol. 20 ( 27 ) 2008.7

Materials design and development of functional materials for industry Reviewed

Asahi Ryoji, Morikawa Takeshi, Hazama Hirofumi, Matsubara Masato

JOURNAL OF PHYSICS-CONDENSED MATTER Vol. 20 ( 6 ) page： 064227 2008.2

Nanostructural characterization of TiNiSn-based half-Heusler compounds Reviewed

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

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

Nanostructural characterization of TiNiSn-based half-Heusler compounds Reviewed

Matsubara M.

International Conference on Thermoelectrics, ICT, Proceedings page： 263 - 266 2007.12

Nitrogen complex species and its chemical nature in TiO2 for visible-light sensitized photocatalysis Reviewed

Asahi Ryoji, Morikawa Takeshi

CHEMICAL PHYSICS Vol. 339 ( 1-3 ) page： 57 - 63 2007.10

Crystallographic orientation analysis on calcium cobaltite ceramic grains textured by reactive-templated grain growth Reviewed

Tani T.

International Journal of Applied Ceramic Technology Vol. 4 ( 4 ) page： 318 - 325 2007.8

Properties of the gold oxides Au2O3 and Au2O: First-principles investigation Reviewed

Shi Hongqing, Asahi Ryoji, Stampfl Catherine

PHYSICAL REVIEW B Vol. 75 ( 20 ) 2007.5

Crystallographic orientation analysis on calcium cobaltite ceramic grains textured by reactive-templated grain growth Reviewed

Tani Toshihiko, Itahara Hiroshi, Kadoura Hiroaki, Asahi Ryoji

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY Vol. 4 ( 4 ) page： 318 - 325 2007

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 Reviewed

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

PHYSICAL REVIEW B Vol. 74 ( 23 ) 2006.12

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

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

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN Vol. 114 ( 1335 ) page： 1022 - 1028 2006.11

Extremely small thermal conductivity of the Al-based Mackay-type 1/1-cubic approximants Reviewed

Takeuchi Tsunehiro, Nagasako Naoyuki, Asahi Ryoji, Mizutani Uichiro

PHYSICAL REVIEW B Vol. 74 ( 5 ) 2006.8

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

Hazama H, Mizutani U, Asahi R

PHYSICAL REVIEW B Vol. 73 ( 11 ) 2006.3

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

Mizutani U, Asahi R, Sato H, Takeuchi T

PHILOSOPHICAL MAGAZINE Vol. 86 ( 3-5 ) page： 645 - 654 2006

Thermoelectric properties of Al-doped ZnO prepared by electrical field-assist sintering Reviewed

Kaga Hisashi, Asahi Ryoji

SCIENCE OF ENGINEERING CERAMICS III Vol. 317-318 page： 811 - 814 2006

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

Asahi R.

International Conference on Thermoelectrics, ICT, Proceedings Vol. 2005 page： 358 - 361 2005.12

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 Reviewed

Asahi R, Sato H, Takeuchi T, Mizutani U

PHYSICAL REVIEW B Vol. 72 ( 12 ) 2005.9

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

Kaga H.

Ceramic Transactions Vol. 167 page： 127 - 136 2005.8

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

Asahi R, Sato H, Takeuchi T, Mizutani U

PHYSICAL REVIEW B Vol. 71 ( 16 ) 2005.4

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

Rhim SH, Kim M, Freeman AJ, Asahi R

PHYSICAL REVIEW B Vol. 71 ( 4 ) 2005.1

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

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

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

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

Kaga H, Asahi R, Tani T

DEVELOPMENTS IN DIELECTRIC MATERIALS AND ELECTRONIC DEVICES Vol. 167 page： 127 - 136 2005

Thermoelectric Properties of Highly Textured Ca-Doped (ZnO)_mIn_2O_3 Ceramics Reviewed

Kaga Hisashi, Asahi Ryoji, Tani Toshihiko

Japanese journal of applied physics. Pt. 1, Regular papers & short notes Vol. 43 ( 10 ) page： 7133 - 7136 2004.10

Thermoelectric Properties of Doped (ZnO)_mIn_2O_3 Reviewed

Kaga Hisashi, Asahi Ryoji, Tani Toshihiko

Japanese journal of applied physics. Pt. 1, Regular papers & short notes Vol. 43 ( 6 ) page： 3540 - 3543 2004.6

First Principles Calculations of Auger Recombination and Impact Ionization Rates in Semiconductors Reviewed

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

JOURNAL OF COMPUTATIONAL ELECTRONICS Vol. 2 ( 2-4 ) page： 197 - 202 2003.12

Growth of In2O3(ZnO)(5) platelet micro-crystals by flux methods Reviewed

Xia CT, Asahi R, Tani T

JOURNAL OF CRYSTAL GROWTH Vol. 254 ( 1-2 ) page： 144 - 150 2003.6

Characterization of Nitrogen-doped Titanium Oxide Photocatalyst Activated by Visible-light Reviewed

OHWAKI Takeshi, MORIKAWA Takeshi, AOKI Koyu, ASAHI Ryoji, TAGA Yasunori, ISOMURA Noritake

Hyomen Kagaku Vol. 24 ( 1 ) page： 25 - 30 2003.1

Language：Japanese Publishing type：Research paper (other academic) Publisher：The Surface Science Society of Japan

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 Reviewed

Picozzi S, Asahi R, Geller CB, Freeman AJ

PHYSICAL REVIEW LETTERS Vol. 89 ( 19 ) 2002.11

Impact Ionization in GaAs within A Screened Exchange Density Functional Formalism Reviewed

Picozzi S.

Journal of Computational Electronics Vol. 1 ( 3 ) page： 421 - 424 2002.10

First-principles calculations for understanding high conductivity and optical transparency in InxCd1-x films Reviewed

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

THIN SOLID FILMS Vol. 411 ( 1 ) page： 101 - 105 2002.5

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

Stampfl C, Asahi R, Freeman AJ

PHYSICAL REVIEW B Vol. 65 ( 16 ) page： 1 - 4 2002.4

Impact ionization in GaAs: A screened exchange density-functional approach Reviewed

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

PHYSICAL REVIEW B Vol. 65 ( 11 ) page： 1 - 4 2002.3

Photocatalysts sensitive to visible light - Response Reviewed

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

SCIENCE Vol. 295 ( 5555 ) page： 627 - 627 2002.1

Electronic structure of misfit-layered calcium cobaltite Reviewed

Asahi R, Sugiyama J, Tani T, Xia CT

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

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

Kim MY, Asahi R, Freeman AJ

JOURNAL OF COMPUTER-AIDED MATERIALS DESIGN Vol. 9 ( 3 ) page： 173 - 201 2002

Electronic structure of misfit-layered calcium cobaltite Reviewed

Asahi R., Sugiyama J., Tani T.

Physical Review B - Condensed Matter and Materials Physics Vol. 66 ( 15 ) page： 1 - 7 2002

Electronic structure of misfit-layered calcium cobaltite Reviewed

Asahi R.

International Conference on Thermoelectrics, ICT, Proceedings Vol. 2002-January page： 203 - 206 2002

Effect of GGA on the half-metallicity of the itinerant ferromagnet CoS2 Reviewed

Shishidou T, Freeman AJ, Asahi R

PHYSICAL REVIEW B Vol. 64 ( 18 ) 2001.11

Electronic structure and small polaron hole transport of copper aluminate Reviewed

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

PHYSICAL REVIEW B Vol. 64 ( 15 ) 2001.10

Computational band-structure engineering of III-V semiconductor alloys Reviewed

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

APPLIED PHYSICS LETTERS Vol. 79 ( 3 ) page： 368 - 370 2001.7

Visible-light photocatalysis in nitrogen-doped titanium oxides Reviewed

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

SCIENCE Vol. 293 ( 5528 ) page： 269 - 271 2001.7

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

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 Vol. 98 ( 13 ) page： 7113 - 7116 2001.6

Band-Gap Narrowing of Titanium Dioxide by Nitrogen Doping Reviewed

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

Japanese journal of applied physics. Pt. 2, Letters Vol. 40 ( 6 ) page： L561 - L563 2001.6

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

Stampfl C, Mannstadt W, Asahi R, Freeman AJ

PHYSICAL REVIEW B Vol. 63 ( 15 ) 2001.4

Band-Gap Narrowing of Titanium Dioxide by Nitrogen Doping. Reviewed

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

Japanese Journal of Applied Physics Vol. 40 ( 6 ) page： L561 - L563 2001

Language：English Publishing type：Research paper (other academic) Publisher：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 Reviewed

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

Physical Review B - Condensed Matter and Materials Physics Vol. 64 ( 18 ) 2001

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

Asahi R, Mannstadt W, Freeman AJ

PHYSICAL REVIEW B Vol. 62 ( 4 ) page： 2552 - 2561 2000.7

Electronic and optical properties of anatase TiO2 Reviewed

Asahi R, Taga Y, Mannstadt W, Freeman AJ

PHYSICAL REVIEW B Vol. 61 ( 11 ) page： 7459 - 7465 2000.3

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

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

PHYSICAL REVIEW B Vol. 61 ( 7 ) page： 4677 - 4684 2000.2

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

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 Vol. 86 ( 1 ) page： 452 - 458 1999.7

Optical properties and electronic structures of semiconductors with screened-exchange LDA Reviewed

Asahi R, Mannstadt W, Freeman AJ

PHYSICAL REVIEW B Vol. 59 ( 11 ) page： 7486 - 7492 1999.3

Micromachined sensors using polysilicon sacrificial layer etching technology Reviewed

Tabata O, Shimaoka K, Asahi R, Sugiyama S

SENSORS AND MATERIALS Vol. 8 ( 1 ) page： 57 - 67 1996

MICROMACHINED SENSORS USING POLYSILICON SACRIFICIAL LAYER ETCHING TECHNOLOGY Reviewed

SUGIYAMA S, TABATA O, SHIMAOKA K, ASAHI R

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

ANISOTROPIC ETCHING OF SILICON IN TMAH SOLUTIONS Reviewed

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

SENSORS AND ACTUATORS A-PHYSICAL Vol. 34 ( 1 ) page： 51 - 57 1992.7

INTEGRATED PYROELECTRIC INFRARED-SENSOR USING PVDF THIN-FILM DEPOSITED BY ELECTRO-SPRAY METHOD Reviewed

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

FERROELECTRIC THIN FILMS III Vol. 310 page： 79 - 84 1992

INFRARED LINEAR IMAGE SENSOR USING A POLY-SI PN JUNCTION DIODE-ARRAY Reviewed

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

INFRARED PHYSICS Vol. 33 ( 4 ) page： 229 - 236 1992

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