Kyushu University [Yuta Tsuji (Assistant Professor) Institute for Materials Chemistry and Engineering, Department of Fundamental Organic Chemistry]

(1) I am conducting the following research subjects at IMCE.
1. Theoretical study on catalytic reactions on metal oxide surfaces.
2. Theoretical study on adhesion interaction at the interface between adhesive resin and metal or inorganic materials
3. Theoretical study on quantum interference in molecular wires
4. Informatics study for the search for catalysts
5. Crystal structure search using swarm intelligence
6. Mixed-anion control of catalytic activity
7. Electronic structure study on electrides

(2) I conduct the instruction of computational chemistry experiment at the experiment courses at Department of Applied Chemistry.
I teach students how to read English literature in chemistry.

(3) I am teaching students in lab. for their bachelor, master, and Ph.D theses.

Research

Research Interests

Theoretical study on catalytic reactions on mixed anion compounds
keyword : metal oxide, mixed anion, methane, density functional theory, catalyst
2019.04.
Graph Theoretic Study on Molecular Conductance
keyword : Graph Theory, Conductance, Adjacency Matrix, Green's Function
2017.12.
Theoretical Study on Catalytic Reactions on Metal-Cluster/Metal Oxide Interface
keyword : Cerium Oxide, Ni cluster, methane, C-H activation
2017.11.
Exploration for New Electride Materials
keyword : Electrides, Database, Density Functional Theory, Band Calculation
2018.06.
Crystal structure search using swarm intelligence
keyword : Crystal structure search, swarm intelligence, density functional theory, band calculation, electride
2018.05.
Informatics study for the search for catalysts
keyword : informatics, methane, density functional theory, metal surfaces
2018.01.
Theoretical study on quantum interference in molecular wires
keyword : molecular wire, conductance, quantum interference, molecular electronics
2018.01.
Theoretical study on adhesion interaction at the interface between adhesive resin and metals
keyword : epoxy resin, gold, adhesion, density functional theory
2018.01.
Theoretical study on adhesion interaction at the interface between adhesive resin and h-BN
keyword : epoxy resin, h-BN, adhesion, density functional theory
2018.01.
Theoretical study on catalytic reactions on metal oxide surfaces
keyword : metal oxide, methane, density functional theory, catalyst
2018.01.

Current and Past Project

The aim of this research is to apply the findings of chemical graph theory to two cutting-edge scientific fields (molecular electronics and cluster catalysis) to analyze and explore materials for advanced devices and catalysts, and to contribute to the development of an information science infrastructure for materials science.

Specifically.
1) We clarify the relationship between electrical conduction behavior and π-conjugate networks in π-conjugated molecular systems whose energy level spectral symmetry is disrupted by hetero-atoms and odd-membered rings.

2) The effect of metal atom networks in clusters on the stabilization of the reaction intermediates is investigated in order to develop catalysts for C1 chemistry using nanoclusters.
In this study, we aim at the theoretical design of the catalytic system to control the catalytic reaction on coordination unsaturated metal on the oxide surface by the presence of anion other than oxide ion. Specifically, the target is the activation of the CH bond that is required for the reforming of methane, which is the main component of natural gas. We work on theoretical research aiming at control of catalytic activity not seen in conventional oxides by controlling the level of d-orbital of coordination unsaturated surface metal site by the concertion of multiple anions.
There exist various algorithms for generating optimum crystal structures. Recently, two groups independently published a convex-hull diagram (an especially convenient way of summarizing thermodynamic preferences) for the lithium–nitrogen system under both standard and high pressures. Ma and co-workers used a structure search method based on the swarm-optimization CALYPSO algorithm. Oganov and co-workers used their variable-composition evolutionary structure prediction tool, the USPEX algorithm. Zunger and co-workers had already performed a structure search for the sodium–nitrogen system by using a global space-group optimization approach, and the convex-hull diagram obtained is quite similar to that of the lithium–nitrogen system.
The existing theoretical searches recover the known nitride as the most stable compound over a range of pressures. The convex-hull diagram also shows that LiN3 should be thermodynamically unstable at standard pressure. Metastable as the azide is, it can be made. On the N-rich side of the Li–N phase diagram, the structure searches have predicted that P63/mmc LiN2 should also be a thermodynamically stable compound.
The wave-particle duality of electrons gives rise to quantum interference (QI) in single molecular devices. A significant challenge to be addressed in molecular electronics is to further develop chemical intuition to understand and predict QI features. In this study, an orbital rule is markedly ameliorated so that it can capture the manifestation of QI not only in alternant hydrocarbons but also in nonalternant ones. The orbital-based prediction about the occurrence of QI in a nonalternant hydrocarbon shows good agreement with experimental results. A simple perturbation theoretic line of reasoning suggests that frontier orbital phase and splitting play a pivotal role in QI phenomena.
Methane, the primary component of natural gas, could play an important role as feedstock to produce value-added chemicals. Since we enjoy abundant supply of natural gas, the last few decades have witnessed a growing requirement for an effective scheme to transform methane to fine commodities. A significant problem chemical industry faces is how one could activate methane. The followings are the major causes why the activation of methane is so intricate. Firstly, the sp3 C-H bond is too strong as exemplified by its large bond dissociation energy (104 kcal/mol). Secondly, its non-polar nature makes it difficult to be trapped in solvents or on surfaces which may catalyze the C-H bond activation. Finally, we need to take care of a problem of overoxidation because the products of the methane functionalization often include a C-H bond which is more reactive than that of methane. For starters, in this paper, we will zero in on the first problem, namely the C-H bond dissociation, because nothing would happen without the C-H bond breaking. In the reactions of methane on most heterogeneous catalysts, this process is regarded as the rate-determining step and researchers are trying very hard to lower the activation barrier for that process.

Academic Activities

Papers

Show All Papers >>

1.	Yuta Tsuji, Mikiya Hori, Kazunari Yoshizawa, Theoretical Study on the Electronic Structure of Heavy Alkali-Metal Suboxides, Inorganic chemistry, 10.1021/acs.inorgchem.9b03046, 59, 2, 1340-1354, 2020.01, On the metal-rich side of the phase diagrams of the Rb-O, Cs-O, and Rb-Cs-O systems, one can find a variety of stoichiometries: for example, Rb₉O₂, Rb₆O, Cs₄O, Cs₇O, Cs₁₁O₃, RbCs₁₁O₃, and Rb₇Cs₁₁O₃. They may be termed heavy alkali-metal suboxides. The application of the standard electron-counting scheme to these compounds suggests the presence of surplus electrons. This motivated us to carry out a theoretical study using the first-principles density functional theory (DFT) method. The structures of these compounds are based on either a formally cationic Rb₉O₂ or Cs₁₁O₃ cluster. The analyses of the partial charge density just below the Fermi level and the electron localization function (ELF) have revealed that there exist surplus electrons in interstitial regions of all the investigated suboxides so that the excess positive charge of the cluster can be compensated. Density of states (DOS) calculations suggest that all of the compounds are metallic. Therefore, the suboxides listed above may be regarded as a new family of metallic electrides, where coreless electrons reside in interstitial spaces and provide a conduction channel. Except for the phases of Rb₉O₂ and Cs₁₁O₃, the suboxide structures include both the cationic clusters and alkali-metal matrix. Several charge analyses indicate that the interstitial surplus-electron density can be assigned to the alkali-metal atoms in the metal matrix, leading to the possibility of the presence of negatively charged alkali-metal atoms, namely Rb^- (rubidide) and Cs^- (caeside) ions, a.k.a. alkalides. In Rb₆O, Rb^-, Rb⁰, and Rb⁺ are found to coexist in the same crystal structure. Similarly, in Cs₇O, one can find the three types of Cs atoms. However, in Cs₄O, no Cs⁰ state is identified. In the Rb-Cs-O ternary suboxides, Rb takes a negatively charged anion state or neutral state, while all of the Cs atoms are found to be cationic because they get involved in the Cs₁₁O₃ cluster and all the Rb atoms exist in interstitial sites. Orbital interactions between the clusters are analyzed to understand how the condensation of the clusters into the solid happens and how the electride nature ensues. These clusters are found to have some superatomic character..
2.	Yuta Tsuji, Wataru Hashimoto, Kazunari Yoshizawa, Lithium-richest phase of lithium tetrelides Li₁₇TT₄ (TT = Si, Ge, Sn, and Pb) as an electride, Bulletin of the Chemical Society of Japan, 10.1246/bcsj.20190040, 92, 7, 1154-1169, 2019.01, The lithium-richest phase in the binary Li-Tt system (Tt = Si, Ge, Sn, and Pb) has a stoichiometry of Li₁₇Tt₄. In the beginning of this paper, the structural complexity of Li₁₇Tt₄ is gradually stripped away using the concept of the M26 cluster found in γ-brass structures and a Tt-centered polyhedral representation. By means of the first-principles electronic structure calculations, which are followed by the analyses of the electron localization function (ELF), Bader charges, and spin density, we observe non-nuclear maxima of the ELF, electron density, and spin density. Since the electron densities off the atoms are confined in crystalline voids, separated from each other, and behaving as an anion, Li₁₇Tt₄ can be identified as a potential zero-dimensional electride. This finding agrees with a simple Zintl picture, which suggests a valence electron count of [(Li⁺)₁₇(Tt⁴¹)₄¢e¹]. Detailed analyses on the band structures, the projected density of states, and crystal orbitals at the ¥ point in the reciprocal space hint at the potential of forming a bond between the non-nuclear electron density and the neighboring atoms. Signatures of bonding and anti-bonding orbital interactions can be witnessed..
3.	Yuta Tsuji, Ernesto Estrada, Ramis Movassagh, Roald Hoffmann, Quantum Interference, Graphs, Walks, and Polynomials, Chemical Reviews, 10.1021/acs.chemrev.7b00733, 118, 10, 4887-4911, 2018.05, In this paper, we explore quantum interference (QI) in molecular conductance from the point of view of graph theory and walks on lattices. By virtue of the Cayley-Hamilton theorem for characteristic polynomials and the Coulson-Rushbrooke pairing theorem for alternant hydrocarbons, it is possible to derive a finite series expansion of the Green's function for electron transmission in terms of the odd powers of the vertex adjacency matrix or Hückel matrix. This means that only odd-length walks on a molecular graph contribute to the conductivity through a molecule. Thus, if there are only even-length walks between two atoms, quantum interference is expected to occur in the electron transport between them. However, even if there are only odd-length walks between two atoms, a situation may come about where the contributions to the QI of some odd-length walks are canceled by others, leading to another class of quantum interference. For nonalternant hydrocarbons, the finite Green's function expansion may include both even and odd powers. Nevertheless, QI can in some circumstances come about for nonalternants from cancellation of odd- and even-length walk terms. We report some progress, but not a complete resolution, of the problem of understanding the coefficients in the expansion of the Green's function in a power series of the adjacency matrix, these coefficients being behind the cancellations that we have mentioned. Furthermore, we introduce a perturbation theory for transmission as well as some potentially useful infinite power series expansions of the Green's function..
4.	Yuta Tsuji, Aleksandar Tsekov Staykov, Kazunari Yoshizawa, Orbital views of molecular conductance perturbed by anchor units, Journal of the American Chemical Society, 10.1021/ja111021e, 133, 15, 5955-5965, 2011.04, Site-specific electron transport phenomena through benzene and benzenedithiol derivatives are discussed on the basis of a qualitative Hückel molecular orbital analysis for better understanding of the effect of anchoring sulfur atoms. A recent work for the orbital control of electron transport through aromatic hydrocarbons provided an important concept for the design of high-conductance connections of a molecule with anchoring atoms. In this work the origin of the frontier orbitals of benzenedithiol derivatives, the effect of the sulfur atoms on the orbitals and on the electron transport properties, and the applicability of the theoretical concept on aromatic hydrocarbons with the anchoring units are studied. The results demonstrate that the orbital view predictions are applicable to molecules perturbed by the anchoring units. The electron transport properties of benzene are found to be qualitatively consistent with those of benzenedithiol with respect to the site dependence. To verify the result of the Hückel molecular orbital calculations, fragment molecular orbital analyses with the extended Hückel molecular orbital theory and electron transport calculations with density functional theory are performed. Calculated results are in good agreement with the orbital interaction analysis. The phase, amplitude, and spatial distribution of the frontier orbitals play an essential role in the design of the electron transport properties through aromatic hydrocarbons..
5.	Yuta Tsuji, Roald Hoffmann, Frontier orbital control of molecular conductance and its switching, Angewandte Chemie - International Edition, 10.1002/anie.201311134, 53, 16, 4093-4097, 2014.04, For transmission of electrons through a π system, when the Landauer theory of molecular conductance is viewed from a molecular orbital (MO) perspective, there obtains a simple perturbation theoretic dependence, due to Yoshizawa and Tada, on a) the product of the orbital coefficients at the sites of electrode attachment, and b) the MO energies. The frontier orbitals consistently and simply indicate high or low transmission, even if other orbitals may contribute. This formalism, with its consequent reinforcement and/or interference of conductance, accounts for the (previously explained) difference in direct vs. cross conjugated transmission across an ethylene, as well as the comparative ON/OFF ratios in the experimentally investigated dimethyldihydropyrene and dithienylethene-type single-molecule switches. A strong dependence of the conductance on the site of attachment of the electrodes in a π system is an immediate extrapolation; the theory then predicts that for some specified sites the switching behavior will be inverted; i.e. the "open" molecular form of the switch will be more conductive. The phase and amplitude of the frontier molecular orbitals at the sites that are connected to electrodes play an essential role in determining transmission of electrons through a π system. When applied to two diarylethene switches, theory then predicts that for some specified sites the switching behavior will be inverted; that is, the "open" molecular form of the switch will be more conductive..
6.	Yuta Tsuji, Ramis Movassagh, Supriyo Datta, Roald Hoffmann, Exponential Attenuation of Through-Bond Transmission in a Polyene Theory and Potential Realizations, ACS Nano, 10.1021/acsnano.5b04615, 9, 11, 11109-11120, 2015.11, An exponential falloff with separation of electron transfer and transport through molecular wires is observed and has attracted theoretical attention. In this study, the attenuation of transmission in linear and cyclic polyenes is related to bond alternation. The explicit form of the zeroth Green's function in a Hückel model for bond-alternated polyenes leads to an analytical expression of the conductance decay factor β. The β values calculated from our model (β_CN values, per repeat unit of double and single bond) range from 0.28 to 0.37, based on carotenoid crystal structures. These theoretical β values are slightly smaller than experimental values. The difference can be assigned to the effect of anchoring groups, which are not included in our model. A local transmission analysis for cyclic polyenes, and for [14]annulene in particular, shows that bond alternation affects dramatically not only the falloff behavior but also the choice of a transmission pathway by electrons. Transmission follows a well-demarcated system of π bonds, even when there is a shorter-distance path with roughly the same kind of electronic matter intervening..
7.	Yuta Tsuji, Roald Hoffmann, Mikkel Strange, Gemma C. Solomon, Close relation between quantum interference in molecular conductance and diradical existence, Proceedings of the National Academy of Sciences of the United States of America, 10.1073/pnas.1518206113, 113, 4, E413-E419, 2016.01, An empirical observation of a relationship between a striking feature of electronic transmission through a π-system, destructive quantum interference (QI), on one hand, and the stability of diradicals on the other, leads to the proof of a general theorem that relates the two. Subject to a number of simplifying assumptions, in a π-electron system, QI occurs when electrodes are attached to those positions of an N-carbon atom N-electron closed-shell hydrocarbon where the matrix elements of the Green's function vanish. These zeros come in two types, which are called easy and hard. Suppose an N+2 atom, N+2 electron hydrocarbon is formed by substituting 2 CH₂ groups at two atoms, where the electrodes were. Then, if a QI feature is associated with electrode attachment to the two atoms of the original N atom system, the resulting augmented N+2 molecule will be a diradical. If there is no QI feature, i.e., transmission of current is normal if electrodes are attached to the two atoms, the resulting hydrocarbon will not be a diradical but will have a classical closed-shell electronic structure. Moreover, where a diradical exists, the easy zero is associated with a nondisjoint diradical, and the hard zero is associated with a disjoint one. A related theorem is proven for deletion of two sites from a hydrocarbon..
8.	Yuta Tsuji, Prasad L.V.K. Dasari, S. F. Elatresh, Roald Hoffmann, N. W. Ashcroft, Structural Diversity and Electron Confinement in Li₄N Potential for 0-D, 2-D, and 3-D Electrides, Journal of the American Chemical Society, 10.1021/jacs.6b09067, 138, 42, 14108-14120, 2016.10, In pursuit of new lithium-rich phases and potential electrides within the Li-N phase diagram, we explore theoretically the ground-state structures and electronic properties of Li₄N at P = 1 atm. Crystal structure exploration methods based on particle swarm optimization and evolutionary algorithms led to 25 distinct structures, including 23 dynamically stable structures, all quite close to each other in energy, but not in detailed structure. Several additional phases were obtained by following the imaginary phonon modes found in low-energy structures, as well as structures constructed to simulate segregation into Li and Li₃N. The candidate Li₄N structures all contain NLi_n polyhedra, with n = 6-9. They may be classified into three types, depending on their structural dimensionality: NLi_n extended polyhedral slabs joined by an elemental Li layer (type a), similar structures, but without the Li layer (type b), and three-dimensionally interconnected NLi_n polyhedra without any layering (type c). We investigate the electride nature of these structures using the electron localization function and partial charge density around the Fermi level. All of the structures can be characterized as electrides, but they differ in electronic dimensionality. Type-a and type-b structures may be classified as two-dimensional (2-D) electrides, while type-c structures emerge quite varied, as 0-D, 2-D, or 3-D. The calculated structural variety (as well as detailed models for amorphous and liquid Li₄N) points to potential amorphous character and likely ionic conductivity in the material..

Presentations

Show All Presentations >>

Yuta Tsuji, Kazunari Yoshizawa, Frontier Orbital Perspective for Electron Transport in Alternant and Nonalternant Hydrocarbons
, ICPAC 2018, 2018.03, The wave-particle duality of electrons gives rise to quantum interference (QI) in single
molecular devices. A significant challenge to be addressed in molecular electronics is to
further develop chemical intuition to understand and predict QI features. In this study, an
orbital rule is markedly ameliorated so that it can capture the manifestation of QI not only in
alternant hydrocarbons but also in nonalternant ones. The orbital-based prediction about the
occurrence of QI in a nonalternant hydrocarbon shows good agreement with experimental
results. A simple perturbation theoretic line of reasoning suggests that frontier orbital phase
and splitting play a pivotal role in QI phenomena..

Membership in Academic Society

Japan Society of Theoretical Chemistry
American Chemical Society
Society of Computer Chemistry,Japan
Japan Society for Molecular Science
The Chemical Society of Japan

Awards

Molecular Understanding of the Adhesive Force between a Metal Oxide Surface and an Epoxy Resin: Effects of Surface Water
Orbital views of molecular conductance perturbed by anchor units
Excellent academic achievement at Faculty of Engineering

Educational

Educational Activities

I conduct the instruction of computational chemistry experiment at the experiment courses at Department of Applied Chemistry.
I teach students how to read English literature in chemistry at Department of Applied Chemistry.

Social

Professional and Outreach Activities

Outreach Activity has done for high school students from Oita prefecture. I taught them the state of the art of quantum mechanics..

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http://trout.scc.kyushu-u.ac.jp/yoshizawaJ/indexE.htmlYoshizawa Laboratory, Institute for Materials Chemistry and Engineering .

https://kyushu-u.pure.elsevier.com/en/persons/yuta-tsuji
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https://sites.google.com/site/tsujiyuta/home
CV .

http://trout.scc.kyushu-u.ac.jp/yoshizawaJ/indexE.html
Yoshizawa Laboratory, Institute for Materials Chemistry and Engineering .