Proton-Exchange Effect of Rb4Ta6O17Crystal on Nitridation Efficiency to Ta3N5 Tetsuya Yamada, Kouhei Machida, Hiroh Miyagawa, Yingjie Chen, Fumitaka Hayashi, et al. Crystal Growth and Design, 2025 (Oxy)nitrides are photocatalysts that can split water under visible-light irradiation. Thus, Ta 3 N 5 is a promising photocatalyst for water splitting. Ta 3 N 5 is typically produced by the nitridation of oxides. However, complete nitridation requires time, and even if it is achieved, the photocatalytic performance is lower than that of a mixture nitrided in the middle. A reason for this is the long-term nitridation, which may induce stepwise nitridation from the surface to the core of the reactant, resulting in overnitridation of the surface composition. To solve this problem, we hypothesized that interlayer interactions in layered oxides affect the nitridation efficiency. This study aimed to verify the role of interlayer interactions in the nitridation of oxides. We demonstrated proton-exchange in Rb 4 Ta 6 O 17 · n H 2 O (RTO) as a model material and its nitridation to Ta 3 N 5 . Consequently, proton-exchange could improve the nitridation efficiency by a factor of 7 compared to nonproton-exchanged RTO. Experimental and theoretical reaction analyses revealed that this improvement was achieved by a change in the reaction pathway and the subsequent structural relaxation of RTO derived from proton exchange. These findings provide new guidelines for developing fast nitridation protocols using ion-exchanged layered oxides.
Tailoring the room-temperature miscibility gap in ordered spinel LiNi0.5Mn1.5O4 cathodes by multi-element doping Shunsuke Narumi, H. Eugenio Otal, Tien Quang Nguyen, Michihisa Koyama, Nobuyuki Zettsu Journal of Materials Chemistry A, 2025 Multi-element doping in LiNi 0.5 Mn 1.5 O 4 (LNMO) cathodes tailors the charge–discharge mechanism from a two-phase to a solid-solution reaction. This reduces lattice strain, suppresses degradation, and enhances long-term battery performance.
Universal neural network potential study of the Pt/CO heterogeneous catalytic system Gerardo Valadez Huerta, Yusuke Nanba, Michihisa Koyama Surfaces and Interfaces, 2025 The high computational costs of DFT methods limit their applicability in studying heterogeneous catalytic systems. Neural network potentials present a promising approach for modelling such systems. In this study, we first validate the use of a universal neural network potential for the Pt(111)/CO system, whose theoretical approach is still under debate, by reproducing experimental CO IR spectra and providing insights into the vibrational modes of adsorbed CO. We further study temperature-dependent single CO adsorption dynamics and oxidation barriers on a Pt 201 nanoparticle . The results show that low barriers require on-top CO and O adsorption at ridge sites, which may be hindered by CO poisoning or strong bridge oxygen adsorption, providing a possible explanation for the experimentally observed slower reaction kinetics at ridges compared to facets. These findings underscore the need for consideration of site distribution on nanoparticles beyond the adsorption and activation properties calculated from slab systems.
Surface steric effect in heterogeneous catalysis as the origin of the high activity induced by strong metal-support interactions Gerardo Valadez Huerta, Kaoru Hisama, Katsutoshi Sato, Katsutoshi Nagaoka, Michihisa Koyama Iscience, 2025 molecules sandwiched between decoration cations on a nanoparticle near the support exhibited a low activation barrier. Our theoretical approach represents a major advancement in bridging the gap between simulation and empirical data and in our understanding of complex supported nanoparticle catalysts.
Elucidation of the Ta(O,N)6 Octahedral Arrangement in Flux-Grown BaTaO2N Photocatalysts by Experimental and Computational Structural Modeling Tetsuya Yamada, Hiroh Miyagawa, Tomohito Sudare, Hiromasa Shiiba, Hideki Tanaka, et al. Inorganic Chemistry, 2025 BaTaO 2 N (BTON) is a visible-light-responsive photocatalyst used for water splitting. The flux method, which involves the use of a molten salt, is an effective synthetic strategy for achieving a high photocatalytic activity. Fluxes with alkali metal cations strongly affect the photocatalytic activity of the BTON crystals. In particular, RbCl flux-grown BTON exhibits hydrogen evolution activity over several times higher than that grown in other chloride fluxes, such as NaCl, under visible-light irradiation. One factor of this difference is presumably owing to the change in the Ta(O,N) 6 octahedral arrangement in the BTON triggered by the doping of alkali metal ions into the crystal lattice. However, the precise Ta(O,N) 6 octahedral arrangement remains unclear. Herein, X-ray absorption spectroscopy, structural analysis by neutron diffraction, and computational structural modeling based on comprehensive structural energy predictions were performed for two types of BTONs. The results suggested that the configuration manners of Ta(O,N) 6 octahedral units strongly depend on the flux composition. Specifically, in NaCl-flux-grown BTON crystals, the number of N20 cis planes parallel to the (100), (010), and (001) crystal planes in a TaO 4 N 2 unit is anisotropic, resulting in differences in their electron–hole conduction characteristics. The findings indicate that in addition to lattice defects, the interconnections of mixed-anion units such as Ta(O,N) 6 should be taken into account to improve the photocatalytic activity of BTONs and develop other mixed-anion compounds.
Molecular Dynamics Simulation of Polymer Electrolyte Membrane for Understanding Structure and Proton Conductivity at Various Hydration Levels Using Neural Network Potential Attila Taborosi, Kentaro Aoki, Nobuyuki Zettsu, Michihisa Koyama, Yuki Nagao Macromolecules, 2025 Alkyl sulfonated polyimides (ASPIs), as alternative polymer electrolytes for fuel cells, are known to exhibit lyotropic liquid crystalline behavior upon water uptake, forming organized lamellar structures and achieving high proton conductivity. Previous experimental studies have shown that ASPIs with planar backbones exhibit enhanced proton conductivity (0.2 S/cm) compared to those with bent backbones (0.03 S/cm). To explain this difference at the atomistic level, molecular dynamics simulations were conducted using a universal neural network potential. The appearance of monomer unit length in planar ASPIs, indicating higher molecular order, was found to correlate with higher proton conductivity compared to that of bent ASPIs. Despite the similar deprotonation and solvation of sulfonic acid groups in both planar and bent ASPIs, the proton conductivity was independent of these factors. Directional mean square displacement analysis provided further insights into the differences in proton conductivity between planar and bent types.
Physical Significance of Descriptors to Predict the Band Center of High-Entropy Nanoalloys Yusuke Nanba, Michihisa Koyama Journal of Computational Chemistry, 2025 The band center of d orbitals ( d ‐band center) has been widely used as an effective descriptor for analyzing material properties. However, in high‐entropy nanoalloys, the diverse atomic environments present challenges in systematically exploring all possible combinations. Due to computational resource limitations, generating a sufficient number of samples is infeasible. Consequently, the d ‐band center should be treated as a response variable in machine‐learning models. We calculated the d ‐band center for individual atoms and applied supervised learning techniques to identify key factors influencing its behavior. While several factors were identified, their physical significance in predicting d ‐band centers remained unclear. To address this issue, we incorporated various interatomic distance terms as descriptors, along with element‐based coordination numbers (ECN). The resulting model closely resembled the overlap integral of the Slater‐type orbital, and the regression coefficients of the ECN exhibited sensitivity to the effective principal quantum number and nuclear charge. Understanding the physical significance of these descriptors is crucial for improving property predictions and facilitating data collection on novel materials.
Design of Active Key Interfaces in Fuel Cells Mori, Toshiyuki, Jiang, San Ping, Shao, Zongping, Koyama, Michihisa, Li, Zhipeng, et al. Design of Active Key Interfaces in Fuel Cells, 2025
Rational Synthesis for a Noble Metal Carbide Takuo Wakisaka, Kohei Kusada, Dongshuang Wu, Tomokazu Yamamoto, Takaaki Toriyama, et al. Journal of the American Chemical Society, 2020
Present status of Japan’s energy Yasunori Kikuchi, Seiichiro Kimura, Michihisa Koyama Energy Technology Roadmaps of Japan Future Energy Systems Based on Feasible Technologies Beyond 2030, 2016
Utilizing risk analysis and scenario planning for technology roadmapping: A case in energy technologies Picmet Portland International Center for Management of Engineering and Technology Proceedings, 2011
Development of novel quantum chemical molecular dynamics simulator and its application to tribochemistry World Tribology Congress 2009 Proceedings, 2009
Effect of misfit angle on superlubricity of molybdenum disulfide: A computational chemistry study World Tribology Congress 2009 Proceedings, 2009
Computational chemistry study on tribochemistry of additive-based solid lubrication World Tribology Congress 2009 Proceedings, 2009
Molecular dynamics of tribochemical reaction with ZDDP Society of Tribologists and Lubrication Engineers 2008 Annual Meeting and Exhibition Extended Abstracts, 2008
Molecular dynamics and quantum chemical molecular dynamics simulations for the design of MgO protecting layer in plasma display panel Proceedings of International Meeting on Information Display, 2008
Trans-disciplinary approach to molecular modeling and experiment in PDP materials Proceedings of International Meeting on Information Display, 2008
A computational study on protecting layer of POP: Secondary electron emission property and surface structure Idw 08 Proceedings of the 15th International Display Workshops, 2008
Excitation energy transfer pathway in Eu-doped BaMgAl10O 17 and NaAl11O17; A theoretical approach Idw 08 Proceedings of the 15th International Display Workshops, 2008
Development of simulators on precise characterization for PDP materials Idw 08 Proceedings of the 15th International Display Workshops, 2008
A theoretical study on chemical reaction of water molecules under laser irradiation: Ultra-accelerated quantum chemical molecular dynamics approach Technical Proceedings of the 2008 Nsti Nanotechnology Conference and Trade Show Nsti Nanotech Nanotechnology 2008, 2008
Effect of surface contamination on destruction and recrystallization dynamics of MgO protecting layer in plasma display panel by molecular dynamics simulation method Idw 07 Proceedings of the 14th International Display Workshops, 2007
Temperature dependency of host emission from BaMgAl10O 17 and its relationship with geometrical structure Idw 07 Proceedings of the 14th International Display Workshops, 2007
Defect levels in BaMgAl10O17 and SrMgAl 10O17: Theoretical and experimental approach Idw 07 Proceedings of the 14th International Display Workshops, 2007
Development of electron emission simulator for protecting layer's surface of plasma display panel Idw 07 Proceedings of the 14th International Display Workshops, 2007
Development of an electrical conductivity simulator for metal oxides based on tight-binding quantum chemistry theory Idw 07 Proceedings of the 14th International Display Workshops, 2007
Development of large-scale quantum chemical molecular dynamics simulator and its application to PDP materials Idw 07 Proceedings of the 14th International Display Workshops, 2007
Development of Monta Program for material and process design in organic electroluminescence and plasma display panel Idw 07 Proceedings of the 14th International Display Workshops, 2007
Quantum chemical molecular dynamics and kinetic Monte Carlo approach to the design of MgO protecting layer in plasma display panel Proceedings of International Meeting on Information Display, 2006
A theoretical analysis of mid-gap states of MgO protecting layer in PDP Idw 06 Proceedings of the 13th International Display Workshops, 2006
Destruction and recrystallization dynamics of MgO protecting layer in plasma display panel by molecular dynamics and quantum chemical molecular dynamics methods Idw 06 Proceedings of the 13th International Display Workshops, 2006
Co-polymerization reaction of ethylene/α-olefin under high temperature and pressure as investigated by a novel dynamics simulator with chemical reaction extension Polymer Preprints Japan, 2006
A study of polymerization processes as investigated by integrated computational chemistry method Polymer Preprints Japan, 2006
Theoretical study of PDF materials Proceedings of International Meeting on Information Display, 2006
Large-scale electronic structure calculation of Eu doped BaMgAI 10O17: Effects of defects on its luminescence properties Idw 06 Proceedings of the 13th International Display Workshops, 2006
Theoretical study of ethylene&1-butene co-polymerization on metallocene catalyst system Polymer Preprints Japan, 2006
A molecular dynamics study on Eu doped BaMgAl10O17: Influence of defects, humidity, and surface on geometrical structure Idw 06 Proceedings of the 13th International Display Workshops, 2006
Robotic path planning and protein complex modeling considering low frequency intra-molecular loop and domain motions. Genome Informatics International Conference on Genome Informatics, 2006
Kinetic Monte Carlo approach to design of MgO protecting layer in plasma display panel Idw AD 05 Proceedings of the 12th International Display Workshops in Conjunction with Asia Display 2005, 2005
Integrated computational chemistry system for the material design of plasma display panel Idw AD 05 Proceedings of the 12th International Display Workshops in Conjunction with Asia Display 2005, 2005
A graph theoretical approach for analysis of protein flexibility change at protein complex formation. Genome Informatics International Conference on Genome Informatics, 2005
Scalable density of states prediction in nanoalloys via machine learning Y Nanba, M Koyama Materials Today Communications, 113871 , 2025 2025
Proton-Exchange Effect of Rb 4 Ta 6 O 17 Crystal on Nitridation Efficiency to Ta 3 N 5 T Yamada, K Machida, H Miyagawa, Y Chen, F Hayashi, M Koyama, ... Crystal Growth & Design 25 (18), 7374-7383 , 2025 2025
Universal neural network potential study of the Pt/CO heterogeneous catalytic system GV Huerta, Y Nanba, M Koyama Surfaces and Interfaces 66, 106542 , 2025 2025 Citations: 2
Surface steric effect in heterogeneous catalysis as the origin of the high activity induced by strong metal-support interactions GV Huerta, K Hisama, K Sato, K Nagaoka, M Koyama Iscience 28 (5) , 2025 2025 Citations: 4
Elucidation of the Ta(O,N) 6 Octahedral Arrangement in Flux-Grown BaTaO 2 N Photocatalysts by Experimental and Computational Structural Modeling T Yamada, H Miyagawa, T Sudare, H Shiiba, H Tanaka, M Takahashi, ... Inorganic Chemistry 64 (14), 6832-6844 , 2025 2025
Support-dependent modulation of Pt33 nanoparticles: Insights into oxygen interaction, stability, electronic properties, and geometric structure M Koyama Surface Science 754, 122686 , 2025 2025 Citations: 2
Physical Significance of Descriptors to Predict the Band Center of High‐Entropy Nanoalloys Y Nanba, M Koyama Journal of Computational Chemistry 46 (8), e70086 , 2025 2025 Citations: 4
Molecular dynamics simulation of polymer electrolyte membrane for understanding structure and proton conductivity at various hydration levels using neural network potential A Taborosi, K Aoki, N Zettsu, M Koyama, Y Nagao Macromolecules 58 (7), 3720-3727 , 2025 2025 Citations: 6
Computational Approach for Designing of Electrode Interfaces in Fuel Cell M Koyama Design of Active Key Interfaces in Fuel Cells, 231-250 , 2025 2025
Structural Stabilization and Superior Electrochemical Performance of Yttrium-Doped O3-NaFe 0.4 Ni 0.3 Mn 0.3 O 2 Cathodes for Sodium-Ion Batteries T Chen, EH Otal, TQ Nguyen, S Narumi, M Koyama, N Zettsu Chemistry of Materials 37 (2), 709-723 , 2025 2025 Citations: 9
Predicting CO Adsorption on Multi-elemental Alloy through Machine Learning Analysis of Ternary Components SM ASPERA, GV HUERTA, Y NANBA, K HISAMA, M KOYAMA Journal of Computer Chemistry, Japan 24 (1), 30-35 , 2025 2025
Tailoring the room-temperature miscibility gap in ordered spinel LiNi 0.5 Mn 1.5 O 4 cathodes by multi-element doping S Narumi, HE Otal, TQ Nguyen, M Koyama, N Zettsu Journal of Materials Chemistry A 13 (30), 25008-25021 , 2025 2025 Citations: 4
Anion Intercalation and Selectivity in NiFe LDH: Insights from Neural Network-Enhanced Molecular Dynamics TQ NGUYEN, SM ASPERA, Y CHEN, K HISAMA, M KOYAMA Journal of Computer Chemistry, Japan 24 (1), 20-26 , 2025 2025 Citations: 1
Data-driven exploration of layered double hydroxide crystals exhibiting high fluoride ion adsorption properties and chemical stability F Hayashi, R Harada, H Sugitani, H Kaneko, TQ Nguyen, M Tipplook, ... CrystEngComm 27 (27), 4677-4685 , 2025 2025 Citations: 1
Element-specific descriptors to predict the stability of binary nanoalloys Y Nanba, M Koyama Computational Materials Science 246, 113336 , 2025 2025 Citations: 6
A comprehensive computer-aided review of trends in heterogeneous catalysis and its theoretical modelling for engineering catalytic activity GV Huerta, K Hisama, M Koyama Journal of Chemical Engineering of Japan 57 (1), 2360928 , 2024 2024 Citations: 2
Molecular dynamics of liquid–electrode interface by integrating Coulomb interaction into universal neural network potential K Hisama, G Valadez Huerta, M Koyama Journal of Computational Chemistry 45 (32), 2805-2811 , 2024 2024 Citations: 4
Theoretical Catalyst Screening of Multielement Alloy Catalysts for Ammonia Synthesis Using Machine Learning Potential and Generative Artificial Intelligence K Hisama, A Ishikawa, SM Aspera, M Koyama The Journal of Physical Chemistry C 128 (44), 18750-18758 , 2024 2024 Citations: 15
Effects of alkyl side chain length on the structural organization and proton conductivity of sulfonated polyimide thin films T Honbo, Y Ono, K Suetsugu, M Hara, A Taborosi, K Aoki, S Nagano, ... ACS Applied Polymer Materials 6 (21), 13217-13227 , 2024 2024 Citations: 5
Extended Unit Cell Model Employing Two Vectors for Crystal Structure Analysis in IrPd Nanoparticles for Catalysis H Ashitani, S Kawaguchi, K Kusada, Y Nanba, SM Aspera, M Koyama, ... ACS Applied Nano Materials 7 (20), 23466-23473 , 2024 2024 Citations: 1
MOST CITED SCHOLAR PUBLICATIONS
Noble-metal high-entropy-alloy nanoparticles: atomic-level insight into the electronic structure D Wu, K Kusada, Y Nanba, M Koyama, T Yamamoto, T Toriyama, ... Journal of the American Chemical Society 144 (8), 3365-3369 , 2022 2022 Citations: 309
Reaction model of dense Sm0. 5Sr0. 5CoO3 as SOFC cathode H Fukunaga, M Koyama, N Takahashi, C Wen, K Yamada Solid State Ionics 132 (3-4), 279-285 , 2000 2000 Citations: 272
Chemical durability of solid oxide fuel cells: influence of impurities on long-term performance K Sasaki, K Haga, T Yoshizumi, D Minematsu, E Yuki, RR Liu, C Uryu, ... Journal of Power Sources 196 (22), 9130-9140 , 2011 2011 Citations: 229
A metal-organic framework as an electrocatalyst for ethanol oxidation L Yang, S Kinoshita, T Yamada, S Kanda, H Kitagawa, M Tokunaga, ... Angewandte Chemie-German Edition 122 (31), 5476 , 2010 2010 Citations: 214
A Computational Chemistry Study on Friction of h-MoS 2 . Part I. Mechanism of Single Sheet Lubrication T Onodera, Y Morita, A Suzuki, M Koyama, H Tsuboi, N Hatakeyama, ... The Journal of Physical Chemistry B 113 (52), 16526-16536 , 2009 2009 Citations: 212
The Mechanism of Porous Sm 0.5 Sr 0.5 CoO 3 Cathodes Used in Solid Oxide Fuel Cells M Koyama, C Wen, T Masuyama, J Otomo, H Fukunaga, K Yamada, ... Journal of the Electrochemical Society 148 (7), A795-A801 , 2001 2001 Citations: 173
Object-based modeling of SOFC system: dynamic behavior of micro-tube SOFC T Ota, M Koyama, C Wen, K Yamada, H Takahashi Journal of Power Sources 118 (1-2), 430-439 , 2003 2003 Citations: 152
Solid‐Solution Alloy Nanoparticles of the Immiscible Iridium–Copper System with a Wide Composition Range for Enhanced Electrocatalytic Applications F Wang, K Kusada, D Wu, T Yamamoto, T Toriyama, S Matsumura, ... Angewandte Chemie International Edition 57 (17), 4505-4509 , 2018 2018 Citations: 123
Tight-binding quantum chemical molecular dynamics simulation of mechano-chemical reactions during chemical–mechanical polishing process of SiO2 surface by CeO2 particle A Rajendran, Y Takahashi, M Koyama, M Kubo, A Miyamoto Applied Surface Science 244 (1-4), 34-38 , 2005 2005 Citations: 115
Development of a new molecular dynamics method for tribochemical reaction and its application to formation dynamics of MoS2 tribofilm Y Morita, T Onodera, A Suzuki, R Sahnoun, M Koyama, H Tsuboi, ... Applied surface science 254 (23), 7618-7621 , 2008 2008 Citations: 102
Battery-assisted low-cost hydrogen production from solar energy: Rational target setting for future technology systems Y Kikuchi, T Ichikawa, M Sugiyama, M Koyama International journal of hydrogen energy 44 (3), 1451-1465 , 2019 2019 Citations: 100
Why solid oxide cells can be reversibly operated in solid oxide electrolysis cell and fuel cell modes? K Chen, SS Liu, N Ai, M Koyama, SP Jiang Physical Chemistry Chemical Physics 17 (46), 31308-31315 , 2015 2015 Citations: 97
Dynamics of Hydrogen Spillover on Pt/γ-Al 2 O 3 Catalyst Surface: A Quantum Chemical Molecular Dynamics Study F Ahmed, MK Alam, A Suzuki, M Koyama, H Tsuboi, N Hatakeyama, ... The Journal of Physical Chemistry C 113 (35), 15676-15683 , 2009 2009 Citations: 92
A CO adsorption site change induced by copper substitution in a ruthenium catalyst for enhanced CO oxidation activity B Huang, H Kobayashi, T Yamamoto, T Toriyama, S Matsumura, ... Angewandte Chemie International Edition 58 (8), 2230-2235 , 2019 2019 Citations: 87
A review of molecular-level mechanism of membrane degradation in the polymer electrolyte fuel cell T Ishimoto, M Koyama Membranes 2 (3), 395-414 , 2012 2012 Citations: 86
Structural stability of ruthenium nanoparticles: a density functional theory study Y Nanba, T Ishimoto, M Koyama The Journal of Physical Chemistry C 121 (49), 27445-27452 , 2017 2017 Citations: 82
A Synthetic Pseudo-Rh: NO x Reduction Activity and Electronic Structure of Pd–Ru Solid-solution Alloy Nanoparticles K Sato, H Tomonaga, T Yamamoto, S Matsumura, NDB Zulkifli, T Ishimoto, ... Scientific reports 6 (1), 28265 , 2016 2016 Citations: 79
Experimental and molecular dynamics simulations of tribochemical reactions with ZDDP: zinc phosphate–iron oxide reaction C Minfray, T Le Mogne, JM Martin, T Onodera, S Nara, S Takahashi, ... Tribology Transactions 51 (5), 589-601 , 2008 2008 Citations: 78
Tribochemical reaction dynamics of phosphoric ester lubricant additive by using a hybrid tight-binding quantum chemical molecular dynamics method M Koyama, J Hayakawa, T Onodera, K Ito, H Tsuboi, A Endou, M Kubo, ... The Journal of Physical Chemistry B 110 (35), 17507-17511 , 2006 2006 Citations: 77
Emergence of high ORR activity through controlling local density-of-states by alloying immiscible Au and Ir K Kusada, D Wu, T Yamamoto, T Toriyama, S Matsumura, W Xie, ... Chemical science 10 (3), 652-656 , 2019 2019 Citations: 67
