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Stacked teacups inspired the idea that columnar assemblies of stacked bowl-shaped molecules may exhibit a unique dynamic behavior, unlike usual assemblies of planar disc– and rod-shaped molecules. On the basis of the molecular design concept for creating higher-order discotic liquid crystals, found in our group, we synthesized a sumanene derivative with octyloxycarbonyl side chains. This molecule forms an ordered hexagonal columnar mesophase, but unexpectedly, the columnar assembly is very soft, similar to sugar syrup. It displays, upon application of a shear force on solid substrates, a flexible bending motion with continuous angle variations of bowl-stacked columns while preserving the two-dimensional hexagonal order. In general, alignment control of higher-order liquid crystals is difficult to achieve due to their high viscosity. The present system that brings together higher structural order and mechanical softness will spark interest in bowl-shaped molecules as a component for developing higher-order liquid crystals with unique mechanical and stimuli-responsive properties.

We present a systematic study clarifying an electronic correlation trend of electrides from first principles. By using the maximally localized Wannier function and the constrained random phase approximation, we calculated the electronic correlation strength $(U-U_{nn})/|t|$ of 19 inorganic electrides, where $U$, $U_{nn}$, and $t$ are the effective onsite Coulomb repulsion, nearest-neighbor Coulomb repulsion, and the nearest-neighbor transfer integrals, respectively. The electronic correlation was found to be highly correlated with the dimensionality of the Wannier-function network of anionic electrons in electrides; the correlation strength varies in the order 0D $>>$ 1D $>$ 2D $\sim$ 3D, showing good correspondence with experimental trends, and exceeds 10 (a measure for the emergence of exotic properties) in all the 0D systems and some of the 1D materials. We also found that the electronic correlation depends on the cation species surrounding the anionic electrons; in the 1D electrides, the electronic correlation becomes stronger for cationic walls consisting of $\mathrm{Ca^{2+}}$, $\mathrm{Sr^{2+}}$, and $\mathrm{Ba^{2+}}$ in this order, and the correlation strength exceeds 10 for $\mathrm{Ba_5As_3}$. The theoretical results indicate that 0- and 1-dimensional electrides will be new research targets for studies on strongly correlated electron systems., 26 pages

Correlated electron materials, such as superconductors and magnetic materials, are regarded as fascinating targets in quantum computing. However, the quantitative resources, specifically the number of quantum gates and qubits, required to perform a quantum algorithm to simulate correlated electron materials remain unclear. In this study, we estimate the resources required for the Hamiltonian simulation algorithm for correlated electron materials, specifically for organic superconductors, iron-based superconductors, binary transition metal oxides, and perovskite oxides, using the fermionic swap network. The effective Hamiltonian derived using the $ab~initio$ downfolding method is adopted for the Hamiltonian simulation, and a procedure for the resource estimation by using the fermionic swap network for the effective Hamiltonians including the exchange interactions is proposed. For example, in the system for the $10^2$ unit cells, the estimated number of gates per Trotter step and qubits are approximately $10^7$ and $10^3$, respectively, on average for the correlated electron materials. Furthermore, our results show that the number of interaction terms in the effective Hamiltonian, especially for the Coulomb interaction terms, is dominant in the gate resources when the number of unit cells constituting the whole system is up to $10^2$, whereas the number of fermionic swap operations is dominant when the number of unit cells is more than $10^3$., 10 pages, 4 figures, 3 tables

In this work, the design, synthesis, and single-molecule conductance of ethynyl- and butadiynyl-ruthenium molecular wires with thioether anchor groups [RS=n-C6 H13 S, p-tert-Bu-C6 H4 S), trans-{RS-(C≡C)n }2 Ru(dppe)2 (n=1 (1R ), 2 (2R ); dppe: 1,2-bis(diphenylphosphino)ethane) and trans-(n-C6 H13 S-C≡C)2 Ru{P(OMe)3 }4 3hex ] are reported. Scanning tunneling microscope break-junction study has revealed conductance of the organometallic molecular wires with the thioacetylene backbones higher than that of the related organometallic wires having arylethynylruthenium linkages with the sulfur anchor groups, trans-{p-MeS-C6 H4 -(C≡C)n }2 Ru(phosphine)4 4n (n=1, 2) and trans-(Th-C≡C)2 Ru(phosphine)4 5 (Th=3-thienyl). It should be noted that the molecular junctions constructed from the butadiynyl wire 2R , trans-{Au-RS-(C≡C)2 }2 Ru(dppe)2 (Au: gold metal electrode), show conductance comparable to that of the covalently linked polyynyl wire with the similar molecular length, trans-{Au-(C≡C)3 }2 Ru(dppe)2 63 . The DFT non-equilibrium Green's function (NEGF) study supports the highly conducting nature of the thioacetylene molecular wires through HOMO orbitals.

Although tin monoxide (SnO) is an interesting compound due to its p-type conductivity, a widespread application of SnO has been limited by its narrow band gap of 0.7 eV. In this work, we theoretically investigate the structural and electronic properties of several SnO phases under high pressures through employing van der Waals (vdW) functionals. Our calculations reveal that a metastable SnO (β-SnO), which possesses space group P21/c and a wide band gap of 1.9 eV, is more stable than α-SnO at pressures higher than 80 GPa. Moreover, a stable (space group P2/c) and a metastable (space group Pnma) phases of SnO appear at pressures higher than 120 GPa. Energy and topological analyses show that P2/c-SnO has a high possibility to directly transform to β-SnO at around 120 GPa. Our work also reveals that β-SnO is a necessary intermediate state between high-pressure phase Pnma-SnO and low-pressure phase α-SnO for the phase transition path Pnma-SnO →β-SnO → α-SnO. Two phase transition analyses indicate that there is a high possibility to synthesize β-SnO under high-pressure conditions and have it remain stable under normal pressure. Finally, our study reveals that the conductive property of β-SnO can be engineered in a low-pressure range (0–9 GPa) through a semiconductor-to-metal transition, while maintaining transparency in the visible light range.

Anion-excess fluorite is a unique structure type of inorganic crystals and is well known as an appropriate crystal structure for fast anion conduction. In particular, the introduction of excess ani...

A conceptually accurate method to connect the free energy multicanonical sampling to meso-scale kinetic Monte Carlo (kMC) dynamics is proposed. The required input parameters for kMC simulation are ...

Topological materials have received much attention because of their intriguing nontrivial physical properties. Their robust topological surface states (TSSs) afford a stable electron bath that facilitates surface reactions, which has been successfully used to promote reactions on transition metals (TMs). As emergent heterogeneous catalysts, TSS-TMs have introduced new catalytic effects. However, the direct application of TSSs to catalysis has thus far remained elusive. In the present study, we show that Bi2Se3, one of the most representative topological insulators, functions as an excellent catalyst for the oxidative carbonylation of amines with CO and O2 to synthesize urea derivatives, showing superior activity compared with conventional TM-containing heterogeneous and homogeneous catalysts. For example, when Bi2Se3 nanoparticles were used as catalysts, the carbonylation of butylamine was completed in 4 h at 20 °C with a yield of 99%, whereas noble-metal-based catalysts do not function at such a low temperature. In addition, the turnover frequency (TOF) of Bi2Se3 (41 h−1) is five times greater than that for BiSe, which has a crystal structure similar to that of Bi2Se3 but with substantially weakened TSSs. Density functional theory calculations further reveal that the TSSs facilitate the activation of O2 through a triplet-to-singlet spin-conversion reaction, which is the key step for the generation of urea derivatives from amines. These findings indicate a new application area of topological insulators in heterogeneous catalysis.

Single-molecule conductance studies on metal-containing inorganic and organometallic molecular wires are relatively less explored compared to those on organic molecular wires. Furthermore, conductance and transmission profiles of the metal-containing wires insensitive to the metal centers often hinder rational design for high performance wires. Here, synthesis and single-molecule conductance measurements of the bis(butadiynyl)rhodium wires with tetracarbene ligands

Conventional MAX phases (M is an early transition metal, A represents a p-block element or Cd, and X is carbon or nitrogen) have so far been limited to carbides and/or nitrides. In the present work...

Ammonia (NH3) is pivotal to the fertilizer industry and one of the most commonly produced chemicals1. The direct use of atmospheric nitrogen (N2) had been challenging, owing to its large bond energy (945 kilojoules per mole)2,3, until the development of the Haber–Bosch process. Subsequently, many strategies have been explored to reduce the activation barrier of the N≡N bond and make the process more efficient. These include using alkali and alkaline earth metal oxides as promoters to boost the performance of traditional iron- and ruthenium-based catalysts4–6 via electron transfer from the promoters to the antibonding bonds of N2 through transition metals7,8. An electride support further lowers the activation barrier because its low work function and high electron density enhance electron transfer to transition metals9,10. This strategy has facilitated ammonia synthesis from N2 dissociation11 and enabled catalytic operation under mild conditions; however, it requires the use of ruthenium, which is expensive. Alternatively, it has been shown that nitrides containing surface nitrogen vacancies can activate N2 (refs. 12–15). Here we report that nickel-loaded lanthanum nitride (LaN) enables stable and highly efficient ammonia synthesis, owing to a dual-site mechanism that avoids commonly encountered scaling relations. Kinetic and isotope-labelling experiments, as well as density functional theory calculations, confirm that nitrogen vacancies are generated on LaN with low formation energy, and efficiently bind and activate N2. In addition, the nickel metal loaded onto the nitride dissociates H2. The use of distinct sites for activating the two reactants, and the synergy between them, results in the nickel-loaded LaN catalyst exhibiting an activity that far exceeds that of more conventional cobalt- and nickel-based catalysts, and that is comparable to that of ruthenium-based catalysts. Our results illustrate the potential of using vacancy sites in reaction cycles, and introduce a design concept for catalysts for ammonia synthesis, using naturally abundant elements. Ammonia is synthesized using a dual-site approach, whereby nitrogen vacancies on LaN activate N2, which then reacts with hydrogen atoms produced over the Ni metal to give ammonia.

Ru-loaded hydrides work as efficient catalysts for ammonia synthesis at low temperatures. The advantages of high activity when using Ru-loaded hydride catalysts are as follows: (i) electron injecti...

Ru-loaded hydride is an efficient catalyst for ammonia (NH3) synthesis under mild conditions. Metal hydrides such as Ca2NH with surface anionic electrons at hydrogen vacancies (Ca2NH1–xex–) functio...

Suzuki cross-coupling reactions catalyzed by palladium are powerful tools for the synthesis of functional organic compounds. Excellent catalytic activity and stability require negatively charged Pd species and the avoidance of metal leaching or clustering in a heterogeneous system. Here we report a Pd-based electride material, Y3Pd2, in which active Pd atoms are incorporated in a lattice together with Y. As evidenced from detailed characterization and density functional theory (DFT) calculations, Y3Pd2 realizes negatively charged Pd species, a low work function and a high carrier density, which are expected to be beneficial for the efficient Suzuki coupling reaction of activated aryl halides with various coupling partners under mild conditions. The catalytic activity of Y3Pd2 is ten times higher than that of pure Pd and the activation energy is lower by nearly 35%. The Y3Pd2 intermetallic electride catalyst also exhibited extremely good catalytic stability during long-term coupling reactions., In Suzuki coupling reactions, excellent catalytic performance require negatively charged Pd species and the avoidance of metal leaching or clustering. Here the authors implanted Pd sites into an intermetallic electride, Y3Pd2, which serves as an efficient and stable catalyst for Suzuki coupling reactions.

Mixed anionic materials such as oxyhydrides and oxynitrides have recently attracted significant attention due to their unique properties, such as fast hydride ion conduction, enhanced ferroelectrics, and catalytic activity. However, high temperature (≥800 °C) and/or complicated processes are required for the synthesis of these compounds. Here we report that a novel perovskite oxynitride-hydride, BaCeO3-xNyHz, can be directly synthesized by the reaction of CeO2 with Ba(NH2)2 at low temperatures (300-600 °C). BaCeO3-xNyHz, with and without transition metal nanoparticles, functions as an efficient catalyst for ammonia synthesis through the lattice N3- and H- ion-mediated Mars-van Krevelen mechanism, while ammonia synthesis occurs over conventional catalysts through a Langmuir-Hinshelwood mechanism with high energy barriers (85-121 kJ mol-1). As a consequence, the unique reaction mechanism leads to enhancement of the activity of BaCeO3-based catalysts by a factor of 8-218 and lowers the activation energy (46-62 kJ mol-1) for ammonia synthesis. Furthermore, isotopic experiments reveal that this catalyst shifts the rate-determining step for ammonia synthesis from N2 dissociation to N-H bond formation.

Fast ionic conductors have considerable potential to enable technological development for energy storage and conversion. Hydride (H−) ions are a unique species because of their natural abundance, light mass, and large polarizability. Herein, we investigate characteristic H− conduction, i.e., fast ionic conduction controlled by a pre-exponential factor. Oxygen-doped LaH3 (LaH3−2xOx) has an optimum ionic conductivity of 2.6 × 10−2 S cm−1, which to the best of our knowledge is the highest H− conductivity reported to date at intermediate temperatures. With increasing oxygen content, the relatively high activation energy remains unchanged, whereas the pre-exponential factor decreases dramatically. This extraordinarily large pre-exponential factor is explained by introducing temperature-dependent enthalpy, derived from H− trapped by lanthanum ions bonded to oxygen ions. Consequently, light mass and large polarizability of H−, and the framework comprising densely packed H− in LaH3−2xOx are crucial factors that impose significant temperature dependence on the potential energy and implement characteristic fast H− conduction., Hydride ions are promising for energy storage since they are abundant, lightweight, and highly mobile, but ionic conductivity should be improved. Here the authors achieve fast hydride ion conductivity in a mixed-anion compound by tuning oxygen content.

Mn+1AXn phases are a large family of compounds that have been limited, so far, to carbides and nitrides. Here we report the prediction of a compound, Ti2InB2, a stable boron-based ternary phase in the Ti-In-B system, using a computational structure search strategy. This predicted Ti2InB2 compound is successfully synthesized using a solid-state reaction route and its space group is confirmed as P$$\bar 6$$ 6 ¯ m2 (No. 187), which is in fact a hexagonal subgroup of P63/mmc (No. 194), the symmetry group of conventional Mn+1AXn phases. Moreover, a strategy for the synthesis of MXenes from Mn+1AXn phases is applied, and a layered boride, TiB, is obtained by the removal of the indium layer through dealloying of the parent Ti2InB2 at high temperature under a high vacuum. We theoretically demonstrate that the TiB single layer exhibits superior potential as an anode material for Li/Na ion batteries than conventional carbide MXenes such as Ti3C2.

Through a first-principles theoretical study, thiol tripods with a rigid C3-symmetric triptycene are proposed as excellent building blocks to achieve well-defined molecule–metal contact. We designed two types of tripods, where three thiol groups are connected to the triptycene skeleton either directly (1) or via a methylene bridge (2), whose geometries fit the lattice structure of Au(111). Structural relaxation of systematically generated initial adsorption configurations of the tripods on Au(111) showed that all three sulfur atoms of 1 and 2 selectively adsorb on fcc hollow and bridge sites, respectively, in such a way that the aromatic blades of triptycene are arranged almost perfectly perpendicular to the metal surface. The absorption energy differences between the most stable and second most stable configurations on Au(111) for 1 (0.126 eV) and 2 (0.298 eV) are larger than the thermal energy at room temperature, indicating excellent site selectivity, particularly for 2.

A state of the art method based on quantum variational algorithms can be a powerful approach for solving quantum many-body problems. However, the research scope in the field is mainly limited to organic molecules and simple lattice models. Here, we propose a workflow of a quantum variational algorithm for periodic systems on the basis of an effective model construction from first principles. The band structures of the Hubbard model of graphene with the mean-field approximation are calculated as a benchmark, and the calculated eigenvalues obtained by restricted Boltzmann machine-based variational quantum eigensolver (RBM-based VQE) show good agreement with the exact diagonalization results within a few meV. The results show that the present computational scheme has the potential to solve many-body problems quickly and correctly for periodic systems using a quantum computer.

In this work, the design, synthesis, and single-molecule conductance of ethynyl- and butadiynyl-ruthenium molecular wires with thioether anchor groups [RS=n-C

Transparent silica glass is an indispensable material for today's information technology society as an ultra-low loss optical fiber. Recently, further low-loss optical fibers are demanded due to rapidly expanding information. A small amount of fluorine doping is known to reduce the Rayleigh scattering further by reducing the density fluctuations of silica glass, even though the fluorine is an impurity for the pristine silica glass. This study devoted to answer the riddle of F-doping and an accurate force-matching potential optimized by machine-learning enables us to understand how fluorine remedies the disorders in silica glass. It was found that fluorine mainly replaces an oxygen in tetrahedral SiO4 unit, but also forms five-fold Si, such as SiO4F and SiO3F2 units. The former disrupts silica network, while the latter attenuates the network rigidity by loosening the five Si-O(F) bonds. Since the two local effects of fluorine spreads through the glass network, F-doping prompts silica glass to relax further even at temperature lower than the glass transition (fictive) temperature. Consequently, fluorine minimizes the density fluctuation (thus, Rayleigh scattering) of silica glass at around 1 wt%, although fluorine itself is an impurity for silica glass.

Control of charge carriers that transport through the molecular junctions is essential for thermoelectric materials. In general, the charge carrier depends on the dominant conduction orbitals and is dominantly determined by the terminal anchor groups. The present study discloses the synthesis, physical properties in solution, and single-molecule conductance of paddle-wheel diruthenium complexes 1R having diarylformamidinato supporting ligands (DArF: p-R-C6H4-NCHN-C6H4-R-p) and two axial thioanisylethynyl conducting anchor groups, revealing unique substituent effects with respect to the conduction orbitals. The complexes 1R with a few different aryl substituents (R = OMe, H, Cl, and CF3) were fully characterized by spectroscopic and crystallographic analyses. The single-molecule conductance determined by the scanning tunneling microscope break junction (STM-BJ) technique was in the 10−5 to 10−4G0 region, and the order of conductance was 1OMe > 1CF3 ≫ 1H ∼ 1Cl, which was not consistent with the Hammett substituent constants σ of R. Cyclic voltammetry revealed the narrow HOMO–LUMO gaps of 1R originating from the diruthenium motif, as further supported by the DFT study. The DFT-NEGF analysis of this unique result revealed that the dominant conductance routes changed from HOMO conductance (for 1OMe) to LUMO conductance (for 1CF3). The drastic change in the conductance properties originates from the intrinsic narrow HOMO–LUMO gaps., Dominant conduction orbitals of paddle-wheel organodiruthenium complexes can be facilely controlled by the substituents embedded in the amidinato ligands.

Here, we report multinuclear organometallic molecular wires having (2,5-diethynylthiophene)diyl-Ru(dppe)2 repeating units. Despite the molecular dimensions of 2–4 nm the multinuclear wires show high conductance (up to 10−2 to 10−3G0) at the single-molecule level with small attenuation factors (β) as revealed by STM-break junction measurements. The high performance can be attributed to the efficient energy alignment between the Fermi level of the metal electrodes and the HOMO levels of the multinuclear molecular wires as revealed by DFT–NEGF calculations. Electrochemical and DFT studies reveal that the strong Ru–Ru interaction through the bridging ligands raises the HOMO levels to access the Fermi level, leading to high conductance and small β values., Multinuclear organometallic molecular wires having (diethynylthiophene)diyl-Ru(dppe)2 repeating units show high conductance with small attenuation factors. The strong Ru–Ru interaction is the key for the long-range carrier transport.

Although tin monoxide (SnO) is an interesting compound due to its p-type conductivity, a widespread application of SnO has been limited by its narrow band gap of 0.7 eV. In this work, we theoretically investigate the structural and electronic properties of several SnO phases under high pressure through employing van der Waals (vdW) functionals. Our calculations reveal that a metastable SnO (A-SnO), which possesses space group P21/c and a wide band gap of 1.9 eV, is more stable than l-SnO at pressures higher than 80 GPa. Moreover, a stable (space group P2/c) and a metastable (space group Pnma) phases of SnO appear at pressures higher than 120 GPa. Energy and topological analyses show that P2/c-SnO has a high possibility to directly transform to t-SnO at around 120 GPa. Our work also reveals that h-SnO is a necessary intermediate state between high-pressure phase Pnma-SnO and low-pressure phase o-SnO for the phase transition path Pnma-SnO ®u-SnO ® g-SnO. Two phase transition analyses indicate that there is a high possibility to synthesize h-SnO under high-pressure conditions and have it remain stable under normal pressure. Finally, our study reveals that the conductive property of -SnO can be engineered in a low-pressure range (0-9 GPa) through a semiconductor-to-metal transition, while maintaining transparency in the visible light range.

We studied the relationship between proton conductivity and the terahertz-regime vibrations of two-dimensional MOFs. The results of spectroscopy studies clarified the essential role played by the collective motions in the terahertz region in 2D layers for efficient H+ conduction. Ab initio calculations suggested the collective motion to be predominantly determined by the valence electronic structure, depending on the identity of the metal ion., Terahertz-regime vibrations of 2D MOFs dominate the intrinsic proton conductivity, and the motions depend on the valence electronic structures.

Self-sorting, in which multiple components selectively assemble themselves by recognising self from others, is an attractive approach to produce supramolecular assemblies with controlled structures. Lock-and-key type complementary physical interactions are required for self-sorting because selective affinity is necessary to distinguish self from others. Here we show self-sorting behaviour based on a principle of geometrical complementarity by shape during our investigation of assembly of pentagonal pillar[5]arenes and hexagonal pillar[6]arenes on a surface. In the homoassembly systems, anionic pillar[5]arenes and pillar[6]arenes are adsorbed onto positively charged layers of cationic pillar[5]arenes and pillar[6]arenes, respectively, through cationic-anionic electrostatic interactions. In contrast, ionic pillar[5]arenes are adsorbed onto layers constructed from oppositely charged pillar[5]arenes, but ionic pillar[6]arenes are not. Equally, for the reverse combination, ionic pillar[6]arenes are adsorbed onto layers constructed from oppositely charged pillar[6]arenes, but ionic pillar[5]arenes are not. The geometrical complementarity by shape realises effective self-sorting even in non-directional multivalent ionic interactions. Self-sorting is an attractive approach to produce complex supramolecular systems and materials with controlled structures. Here the authors show geometrical complementarity in the self-sorting behaviour of pentagonal and hexagonal pillararenes on heterogeneous surface through layer-by-layer deposition.

Ammonia decomposition is an important technology for extracting hydrogen from ammonia toward the realization of a hydrogen economy. Herein, it is reported that large oblate hemispheroidal Ru particles on Ca(NH2 )2 function as efficient catalysts for ammonia decomposition. The turnover frequency of Ru/Ca(NH2 )2 increased by two orders of magnitude when the Ru particle size was increased from 1.5 to 8.4 nm. More than 90 % ammonia decomposition was achieved over Ru/Ca(NH2 )2 with large oblate hemispheroidal Ru particles at 360 °C, which is comparable to that of alkali-promoted Ru catalysts with small Ru particle sizes. XAFS analyses revealed that Ru particles are immobilized on Ca(NH2 )2 by Ru-N bonds formed at the metal/support interface, which lead to oblate hemispheroidal Ru particles. Such a strong metal-support interaction in Ru/Ca(NH2 )2 is also substantiated by DFT calculations. The high activity of Ru/Ca(NH2 )2 with large Ru particles primarily originates from the shape and appropriate size of the Ru particles with a high density of active sites rather than the electron-donating ability of Ca(NH2 )2 .

Ruthenium is the most effective catalyst reported to date for ammonia synthesis under mild conditions, especially when an electron promoter is used. However, electron donation from the promoter has not been sufficient because the promoter contacts with Ru only through its surface. Here, we report a Laves phase intermetallic bulk catalyst, YRu2, which has higher electron density on Ru. This is derived from large electron transfer from Y to Ru, which is first confirmed by X-ray absorption fine structure measurements and theoretical calculations. In addition, YRu2 has high hydrogen solubilities leading to suppression of hydrogen poisoning, a common drawback of Ru-based catalysts. Consequently, YRu2 exhibits higher catalytic activity for ammonia synthesis over 300 times that with pure ruthenium. The present results suggest a simple concept for ammonia synthesis: Laves phase intermetallic compounds of Ru and more electropositive metals are more efficient catalysts than pure Ru because of the large electron pro...

A low-temperature ammonia synthesis process is required for on-site synthesis. Barium-doped calcium amide (Ba-Ca(NH2 )2 ) enhances the efficacy of ammonia synthesis mediated by Ru and Co by 2 orders of magnitude more than that of a conventional Ru catalyst at temperatures below 300 °C. Furthermore, the presented catalysts are superior to the wustite-based Fe catalyst, which is known as a highly active industrial catalyst at low temperatures and pressures. Nanosized Ru-Ba core-shell structures are self-organized on the Ba-Ca(NH2 )2 support during H2 pretreatment, and the support material is simultaneously converted into a mesoporous structure with a high surface area (>100 m2 g-1 ). These self-organized nanostructures account for the high catalytic performance in low-temperature ammonia synthesis.

The effects of cation dopants in zirconia on the H2 oxidation mechanism at the pore/nickel/zirconia triple phase boundary (TPB) were theoretically examined. Y, Sc, Al, Ce, and Ca were considered as dopants, and on-boundary, O-migration, and H-migration reaction mechanisms were examined. Based on density functional theory calculations, Y as a dopant favored the on-boundary mechanism with water molecule formation within the immediate proximity of the TPB. The corresponding rate-limiting step is H transfer from the nickel surface to the boundary. In contrast, the on-boundary mechanism is not completed with the Al-, Sc-, and Ca-doped systems, due to the dissociation of water molecules at the boundary. In the Al-doped system, the O-migration mechanism is the major reaction pathway due to a low barrier for the rate-limiting step that corresponds to O transfer from zirconia to the nickel surface. The H-migration mechanism, which implies water molecule formation on the zirconia surface at a position distant from the boundary, should dominate at the Sc-, Ca-, and Ce-doped TPBs, with the lowest activation barrier at the Sc-doped TPB. The reasons for the switching of the reaction mechanisms depending on the dopant species are analyzed.

We proposed a multi-scale computational framework based on a wave-packet propagation with a non-linear tight-binding Huckel model and molecular dynamics with a density functional method, and adopted the multi-scale approach to carrier transport of organic polymers showing dynamic structural fluctuations. In the tight-binding Huckel Hamiltonian, we introduced an electron–hole binding energy, the non-linear term in the present method, and investigated the influence of the electron–hole binding on the carrier mobility. We conducted wave-packet propagation for 5 ps dynamics on two kinds of polymers with 1 μm length. We found that when the electron–hole binding energy is changed from 0 to 500 meV, the carrier mobility can be changed by two orders of magnitude. We also analyzed the localization property of the wave-packet on the polymers, and found that (1) in both small and large electron–hole binding regimes, the orbital localization simply causes the decrease in carrier mobility, and (2) in an intermediate electron–hole binding regime, the orbital localization rather enhances the carrier mobility.

We succeeded in the synthesis of an anionic stannaferrocene by the reaction of a dilithiostannole with a Fe(III) reagent, which cannot be achieved by the use of cyclopentadienyl (Cp) and its relate...

Key functions for the stability and activity of Ru catalysts for ammonia synthesis were examined by x-ray absorption fine structure (XAFS) experiments. Ru K-edge XAFS measurements were carried out for two Ru catalysts, Ru/Ca2NH and Ru/CaNH, which include N atoms in the supports. The stable Ru-N bond was observed in the Ru/Ca2NH catalyst, but not in the Ru/CaNH catalyst, which was also supported by theoretical calculations in terms of Ru--anion bond strength. The bond observed in the Ru/Ca2NH works to anchor the Ru nanoparticles to the Ca2NH support, and the activity has been maintained. Formation of anchoring bonds between catalyst particles and supports is essential to create highly active and long lasting catalysts.

A one-dimensional microkinetic model combining H and O migration mechanisms is used to simulate the surface diffusion, chemical and charge-transfer reactions near the triple phase boundary of the Ni/YSZ patterned anode. A number of parameter sets are exhaustively examined in the microkinetic schemes to obtain a proper set for the explanation of experimental observations. We find a set of parameters free from unphysical fitting parameters, and can explain a large activity gap of patterned anodes reported in literature. From our simulation, we found that the lower activity patterned anode is kinetically governed by both H and O migration across the triple phase boundary, while the higher activity patterned anodes are governed by the O migration.

The outstanding developments of computers and theoretical methods especially on first principles electronic structure calculations enable us to investigate the stability and reactivity of bulk materials and hetero interfaces in atomistic scale with high precision, although we still have limitations on the time domain and system size. If we can extensively extend the accessible regions about time domain and system size in atomistic simulations at the same time, it will be a further development in computer simulations for materials designing. In order to realize such an extended computational tool, we have been developing a full atomistic kinetic Monte Carlo code which can easily incorporate kinetic date from first principles calculations. The characteristic points in the kMC code are 1) parallelization in domain decomposition scheme, 2) easy constructions of hetero structures and reactions, 3) boundary conditions including open-boundary, 4) Poisson solver, and 5) direct counting of flowing current. Points 1, 2, and 3 (partly) were already described in our previous paper [1]. The standard cases for the developed kMC execution in a single computer are roughly μs-to-ms time domain for 1 million atoms. Although the size in the kMC might seem to be not so large, the atomistic system represented in kMC cell is defined as a function of electrochemical potential, together with thermodynamic parameters (i.e., temperature and pressure) and chemical conditions such as dopant conditions. That is, the kMC cell can be regarded as a semi-infinite system, and thus the problems on the size limitation is technically avoided. To explain this point in more detail, let’s consider a whole SOFC system composed of anode (A), solid electrolyte (SE), and cathode (C). The chemical composition in deep inside of SE can be regarded as a stoichiometric one even at a working situation with no degradation, and this is of course true at around equilibrium conditions, OCV. On the other hand, the compositions of interfaces A/SE and C/SE can be significantly deviated from the stoichiometry, depending on the thermodynamic conditions. Our kMC can handle the hetero interfaces A/SE and C/SE smoothly connected with stoichiometric SE in the kMC computational cell. That’s why the size limitation cannot be so problematic; it should be mentioned that we can also handle the whole system of A-SE-C in one kMC computational cell when the thickness of SE is too small to realize an equilibrium composition at the inside of SE. To check the reliability of the developed kMC code, we applied it to the calculations of electromotive force (EMF) of oxide concentration cells, and compared the calculated EMF with that obtained from Nernst equation. We adopted 8mol% doped YSZ as SE. In the EMF calculations, the direct counting approach of ionic current, one of the characteristic points in our kMC, was used to find OCV condition depending on gas partial pressures. As a result, we found the excellent agreements between simulated EMF and ideal EMF from Nernst equation. This means that the reliability of our kMC dynamics in the atomistic model is guaranteed in terms of thermodynamics because the equilibrium situations and steady states in the concentration cells are recognized using ionic motions (i.e., direct counting) in kMC. The details of calculated results and computational algorisms especially for direct counting and open-boundary condition will be explained in the conference. Reference [1] T. Tada and N. Watanabe, ECS Transactions 57(1), 2437-2447 (2013).

Recently, the successful synthesis of two-dimensional (2D) boron on metallic surfaces has motivated great interest in improving the stability of 2D boron to allow the realization of promising materials. Through the use of an ab initio evolutionary search algorithm, we have discovered a series of TiBx (2 ≤ x ≤ 16) structures that consist of earth-abundant titanium and boron atoms in 2D arrangements. These structures are greatly stabilized by electron transfer from Ti to B, therefore, leading to much better stability than the 2D boron sheets proposed so far. In particular, TiB12 has a low enough energy to make it competitive to a mixture of the well-known TiB2 compound and a 2D α-boron sheet and exhibits a quasi-Dirac point with a 0.02 eV gap. Interestingly, the work function and conductivity of this 2D TiB12 material are calculated to be tunable through the application of biaxial strain. The possibility of synthesis and novel electronic properties expected for 2D TiB12 render it a promising new 2D material for nanoelectronic applications.