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

Dynamic lateral transport of lipids, proteins, and self-assembled structures in biomembranes plays a crucial role in diverse cellular processes. In this study, we perform coarse-grained molecular dynamics simulations on a vesicle composed of a binary mixture of neutral and anionic lipids to investigate the lateral transport of individual lipid molecules and the self-assembled lipid domains upon an applied direct current (DC) electric field. Under the potential force of the electric field, a phase-separated domain rich in anionic lipids is trapped in the opposite direction of the electric field. The subsequent reversal of the electric field induces unidirectional domain motion. During the domain motion, the domain size remains constant, but a considerable amount of the anionic lipids is exchanged between the anionic-lipid-rich domain and the surrounding bulk. While the speed of the domain motion (collective lipid motion) shows a significant positive correlation with the electric field strength, the exchange of anionic lipids between the domain and bulk (individual lipid motion) exhibits no clear correlation with the field strength. The mean velocity field of the lipids surrounding the domain displays a two-dimensional (2D) source dipole. We revealed that the balance between the potential force of the applied electric field and the quasi-2D hydrodynamic frictional force well explains the dependence of the domain motions on the electric field strengths. The present results provide insight into the hierarchical dynamic responses of self-assembled lipid domains to the applied electric field and contribute to controlling the lateral transportation of lipids and membrane inclusions.

DOI： 10.1021/acs.jpcb.3c04351

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記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：RSC Advances  

γ-Carbonyl-substituted ε-caprolactones were found to predominantly isomerize to five-membered lactones rather than to form desired linear polyesters in ring-opening polymerization.

DOI： 10.1039/d3ra01025b

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記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：Structural Dynamics  

The dynamics of hydration water (HW) in 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE) was investigated by means of quasi-elastic neutron scattering (QENS) and compared with those observed in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). The headgroup dynamics of DMPE was investigated using a mixture of tail-deuterated DMPE and D2O, and the QENS profiles were interpreted as consisting of three modes. The fast mode comprised the rotation of hydrogen atoms in –NH3+ and –CH2– groups in the headgroup of DMPE, the medium-speed mode comprised fluctuations in the entire DMPE molecule, and the slow mode comprised fluctuations in the membrane. These interpretations were confirmed using molecular dynamics (MD) simulations. The HW dynamics analysis was performed on a tail-deuterated DMPE and H2O mixture. The QENS profiles were analyzed in terms of three modes: (1) a slow mode, identified as loosely bound HW in the DMPC membrane; (2) a medium-speed mode similar to free HW in the DMPC membrane; and (3) a fast mode, identified as rotational motion. The relaxation time for the fast mode was approximately six times shorter than that of rotational water in DMPC, consistent with the results of terahertz time-domain spectroscopy. The activation energy of medium-speed HW in DMPE differed from that of free HW in DMPC, suggesting the presence of different hydration states or hydrogen-bonded networks around the phosphocholine and phosphoethanolamine headgroups.

DOI： 10.1063/4.0000184

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記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：Soft Matter  

Correlation between the phase separation of membranes consisting of negatively charged and neutral phospholipids and cation distribution in aqueous solutions is presented.

DOI： 10.1039/d3sm00222e

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記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the American Chemical Society  

Biological membranes are functionalized by membrane-associated protein machinery. Membrane-associated transport processes, such as endocytosis, represent a fundamental and universal function mediated by membrane-deforming protein machines, by which small biomolecules and even micrometer-size substances can be transported via encapsulation into membrane vesicles. Although synthetic molecules that induce dynamic membrane deformation have been reported, a molecular approach enabling membrane transport in which membrane deformation is coupled with substance binding and transport remains critically lacking. Here, we developed an amphiphilic molecular machine containing a photoresponsive diazocine core (AzoMEx) that localizes in a phospholipid membrane. Upon photoirradiation, AzoMEx expands the liposomal membrane to bias vesicles toward outside-in fission in the membrane deformation process. Cargo components, including micrometer-size M13 bacteriophages that interact with AzoMEx, are efficiently incorporated into the vesicles through the outside-in fission. Encapsulated M13 bacteriophages are transiently protected from the external environment and therefore retain biological activity during distribution throughout the body via the blood following administration. This research developed a molecular approach using synthetic molecular machinery for membrane functionalization to transport micrometer-size substances and objects via vesicle encapsulation. The molecular design demonstrated in this study to expand the membrane for deformation and binding to a cargo component can lead to the development of drug delivery materials and chemical tools for controlling cellular activities.

DOI： 10.1021/jacs.2c12348

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記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：Macromolecules  

Poly(ethylene glycol)-conjugated amphiphilic block copolymers, which contain degradable hydrophobic blocks connected by a rigid hydrogen-bonding motif (RHM), are developed to yield anisotropic nanoassemblies in a manner independent of the crystalline nature of the hydrophobic block. The all-atom and coarse-grained molecular dynamics simulations suggest that the anisotropic alignment of the block copolymers can be attributed to the π-πinteractions of the RHM and the crystallizable hydrophobic blocks help maintain the aligned structure. Light scattering analysis of the polymer assemblies demonstrates the formation of nonspherical assemblies by the RHM-containing block copolymers with an amorphous hydrophobic block; this indicates the strong contribution of the RHM to the directed assembly of the block copolymers, unlike crystallization-driven self-assembly. Enhanced cell proliferation is observed in cell cultures containing normal human fibroblasts in the presence of the anisotropic polymer assemblies with aspect ratios greater than 12 or lengths greater than 310 nm.

DOI： 10.1021/acs.macromol.1c01894

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記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemical Communications  

Self-sorting and co-assembly of aqueous supramolecular fibres were formed using peptide amphiphiles having immiscible hydrophobic tails.

DOI： 10.1039/d1cc05560g

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記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acsami.1c09468

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acs.langmuir.1c00967

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acs.langmuir.1c00727

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acs.langmuir.1c00417

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.1103/physreve.103.042502

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.1039/d0cp05826b

記述言語：その他   掲載種別：研究論文（学術雑誌）  

We reveal the generation of the "Graphene Arch-Bridge"on a diamond (111) surface by Si doping via first-principles calculations. The "Graphene Arch-Bridge"is different from a simple graphene structure because both its ends are pinned to the diamond surface, and it has an interesting arched-type curved structure. The large stress around the doped Si atom leads to the transition of the six-membered C ring to a five-membered C ring. The C atom excluded from the ring by this transition changes from an sp3 carbon to an sp2 carbon and generates the "Graphene Arch-Bridge"on the diamond (111) surface. These results suggest that the generation of the five-membered C ring by stress due to the Si doping is the reason why the "Graphene Arch-Bridge"is generated. Finally, we propose that the "Graphene Arch-Bridge"is the origin of the experimentally observed super-low friction of Si-doped diamond-like carbon (DLC). Furthermore, we suggest that the "Graphene Arch-Bridge"leads to the lower wear properties of Si-doped DLC compared with nondoped DLC because its ends of the bridge are pinned to the DLC surface.

DOI： 10.1021/acs.jpcc.0c09716

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.1246/cl.200323

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acs.biomac.0c01095

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1126/sciadv.aax9301

記述言語：その他   掲載種別：研究論文（学術雑誌）  

Stress Transmitters at the Molecular Level in the Deformation and Fracture Processes of the Lamellar Structure of Polyethylene via Coarse-Grained Molecular Dynamics Simulations

DOI： 10.1021/acs.macromol.9b00636

記述言語：その他   掲載種別：研究論文（学術雑誌）  

Coarse-grained molecular dynamics simulation for uptake of nanoparticles into a charged lipid vesicle dominated by electrostatic interaction

DOI： 10.1103/PhysRevE.100.012407

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Ionic Conductivity in Ionic Liquid Nano Thin Films
PMID: 30199622

DOI： 10.1021/acsnano.8b06386

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.1246/cl.180450

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.carbon.2018.03.034

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1038/s41428-018-0067-1

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.jcat.2018.03.017

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DOI： 10.1021/acs.macromol.8b00124

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acsami.7b07551

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acsami.7b07737

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acs.macromol.6b02613

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1038/srep46394

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Effect of Polarity of a Substrate on ZnO Crystal Growth Process by Molecular Dynamics Simulation

DOI： 10.2477/jccj.2016-0056

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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DOI： 10.1103/PhysRevE.94.042611

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1088/0965-0393/24/5/055006

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acsami.5b11910

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1039/c5cp06515a

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acs.jpcc.5b08561

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1103/PhysRevE.92.062713

記述言語：日本語  

Development and application of a double-network gel modeling method for fracture processes using a coarse-grained molecular dynamics simulation
We examine the mechanism of fracture processes in a double-network (DN) gel model by using a coarse-grained molecular dynamics simulation. Initially, we develop a modeling method for DN gel containing both slightly and highly cross-linked networks, and then stretch the DN gel model. During stretching, the highly cross-linked network begins to dissociate at a strain of 1.0, increasing the stress. At strains from 4.0 to 5.0, the slightly and highly cross-linked networks simultaneously dissociate and the stress decreases. Then, the dissociation of the highly cross-linked network stops and only the slightly cross-linked network dissociates at a strain of 12.0, while the stress remains almost the same. We reveal that characteristics of each type of network gradually appear in the DN gel. Next, we change the polymer chain length to reveal its influence on the mechanical properties of the gel. An increase in the length of the slightly cross-linked network chains improves the strength of the DN gel, whereas that of the highly cross-linked network chains does not affect its strength. An increase in the slightly cross-linked network chain length increases the number of entanglements, leading to the increase in strength.

DOI： 10.2477/jccj.2015-0053

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.1039/c5ta05575j

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.chemphys.2015.08.007

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acs.jpcc.5b01370

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

DOI： 10.1149/06801.3187ecst

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1038/srep09052

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：その他  

Tribo-Chemical Reaction of Molybdenum Dithiocarbamate on Diamond-Like Carbon Films: Quantum Chemical Molecular Dynamics Simulation

DOI： 10.2477/jccj.2014-0034

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/jp5015252

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1039/c4ra04065a

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/jp503331e

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/jp412461q

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.4869515

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

DOI： 10.1149/05701.2459ecst

記述言語：その他  

Quantum chemical molecular dynamics simulation on atomistic mechanisms of SiO2 etching process by fluorocarbon radicals

記述言語：英語  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/jp4021504

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/jp310920d

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.7567/JJAP.52.026502

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/jp3002542

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1039/c2fd00125j

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1103/PhysRevE.84.021924

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1103/PhysRevE.82.031909

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.ultramic.2010.02.032

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.cplett.2008.06.068

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.2759925

記述言語：その他  

Conformational Hysteresis on A Giant DNA Molecule

開催年月日： 2022年5月

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Fracture Process of Polymer Materials by Molecular Simulation

開催年月日： 2022年5月

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Mechanical Properties of Semicrystalline Polymers at the Molecular Level by Coarse-Grained Molecular Dynamics Simulation

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記述言語：日本語  

We performed the chemical mechanical polishing (CMP) process simulations of GaN(0001) by a SiO_2 cluster in aqueous NaOH and H_2O_2 solution. In aqueous NaOH solution, OH" ions adsorbed on the Ga-top site of the GaN surface. In aqueous H_2O_2 solution, OH radicals adsorbed on the hollow site of the GaN surface and weakened the Ga-N back-bond. Therefore, we suggest that the OH radical is effective for GaN-CMP as compared with the OH ion. However, we did not observe the subsequent chemical reactions and the polishing process of the GaN surface in both environments. We performed the CMP process simulation of GaN(0001) by a SiO_2 cluster with many OH radicals produced by a catalyst. After the OH radicals occupied all the hollow sites of the GaN surface, and another OH radical attacked a Ga atom of GaN surface, we observed the diffusion of the OH species adsorbed on the GaN surface into the GaN bulk and generation of gallium oxide and N_2 molecules.

記述言語：日本語  

Friction of silicon carbide (SiC) films under water environment shows a low friction coefficient experimentally. Understanding of the mechanism is essential to improve friction characteristics of the SiC films. However, it is difficult to directly obtain atomic-scale dynamics with chemical reactions by experiments. In this study, our purpose is to reveal the chemical reactions of the SiC surface under water lubrication by our first-principles molecular dynamics (FPMD) and tight-binding quantum chemical molecular dynamics (TB-QCMD) methods. First, we performed the simulation of SiC sliding in water by our FPMD method and then Si-OH and C-H bonds were generated on the surface. Next, we also simulated the larger model of SiC in water environment by our TB-QCMD method. Then, the generation of Si-O-Si bonds and the growth of Si-O-Si bond chains were observed. We suggest that this growth relates to the low friction property of the SiC surface.

記述言語：英語  

Si doped DLC films as solid lubricant exhibit excellent tribological properties of low friction and high wear resistance. One of the low friction reasons is the structure change from sp^3 carbon to sp^2 carbon on the surface of DLC films by Si doping. In this study, to reveal the mechanism of the structure change of the DLC surface by Si doping, we investigate the surface structure of the Si doped diamond using the first-principles calculation. The results show the structure change from six-membered ring to five-membered ring on the surface of Si doped diamond since a Si atom has larger atomic radius than a C atom. Furthermore, the structure change from sp^3 carbon to sp^2 carbon results in the generation of graphene, which would affect the low friction of Si doped DLC films.

記述言語：日本語  

We performed friction simulations of hydrogen terminated carbon nitride (H-CNX) using our first-principles molecular dynamics (FPMD) and tight-binding quantum chemical molecular dynamics (TB-QCMD) simulators. In FPMD simulation, H-CN_X showed low friction coefficient of 0.15 and 0.10 at 5 and 10 GPa, respectively. This is because terminated hydrogen atoms prevented the bond generation at the films interface. In TB-QCMD simulation, under 1 GPa, H-CN_X and H-DLC also showed low friction coefficients of 0.05 because terminated hydrogen atoms prevented the bond generation at the films interface. On the other hand, under 5 GPa, while H-CN_X showed a low friction coefficient of 0.07, a friction coefficient of H-DLC takes a high value of 0.42. Although C-C bonds were generated at the interface of H-DLC films under high pressure, nitrogen atoms of H-CN_X prevented C-C bond generation at the interface. We found that H-CN_X is more stable and shows lower friction than H-DLC under high pressure.

記述言語：日本語  

In order to reveal a chemical mechanical polishing (CMP) mechanism of a sapphire substrate by a colloidal silica abrasive grain, we investigated a polishing process of an α-Al_2O_3(0001) surface by a SiO_2 cluster under water environment by a first-principles calculation. The results show that the mechanical pressing by the SiO_2 cluster and the chemical reaction with a H_2O molecule introduce the break of the Al-O bond of the α-Al_2O_3(0001) surface. In addition, after the chemical reaction with H_2O, an Al(OH)_3 molecule is generated and desorbs from the α-Al_2O_3 surface in the CMP process.

記述言語：日本語  

To clarify the degradation mechanism of the perfluorinated polymer electrolytes in polymer electrolyte fuel cells, we studied the decomposition process of the end group of these polymers using the first-principles molecular dynamics method. We successfully clarified that the polymer end model of CF_3CF_2CF_2OH reacts with a hydroxyl radical to generate a water molecule and CF_2O. After CF_2O was desorbed, polymer end model became CF_3CF_2・. CF_3CF_2・reacts with another hydroxyl radical to reproduce the hydroxyl end group. Therefore, it was revealed that cyclic degradation reactions like the unzipping mechanism occur when CF_3CF_2CF_2OH reacts with hydroxyl radicals. Furthermore, it was revealed that the CF_2O desorption reaction is inhibited by surrounding water molecules, while the HF desorption reaction from CF_3CF_2CF_2OH is promoted.

記述言語：日本語  

A PtRu alloy nano-particle attracts attention as an anode catalyst in a polymer electrolyte fuel cell because of its higher tolerability for CO poisoning than a Pt nano-particle. To reveal the mechanism of the high tolerability for CO in the PtRu alloy nano-particle, we investigated adsorption process of a CO molecule on the Pt and PtRu alloy nano-particles by first-principles calculation. The results show that the bond length of the CO molecule adsorbed on the PtRu alloy nano-particle is longer than that on the Pt nano-particle. This indicates that the PtRu alloy nano-particle oxidizes a CO molecule to a CO_2 molecule more easily than the Pt nano-particle. In addition, the CO molecule is more difficult to adsorb on the Pt atom in the PtRu alloy nano-particle than that in the Pt nano-particle.

記述言語：日本語  

We study the degradation process and toughness of polymer composites by first-principles calculation and coarse-grained molecular dynamics simulation. To clarify the effect of water at the filler surface on the degradation of polymers, we calculate H abstraction of polyethylene by OH and H radicals. Activation barriers are 3.2 and 5.0 kcal/mol and these reactions easily occur at room temperature. Therefore, water molecules generate radical and cause degradation. Then, we study the toughness of melt and semicrystalline polymers with filler against the stretching by coarse-grained molecular dynamics simulation. In melt polymer, fillers increase the toughness but the toughness of degraded one decrease more than that without fillers. On the other hand, in semicrystalline polymer, fillers decrease the toughness but the toughness of degraded one decrease less than that without fillers.

記述言語：日本語  

To develop the inexpensive non-noble highly-active and selective catalyst of the alkaline fuel cell (AFC), we investigated ethylene glycol oxidation on transition metal surfaces such as Fe(001), Co(0001), and Ni(111) based on first principles calculation. To clarity which surface has high activity for ethylene glycol oxidation, we calculate the activation energies for O-H and C-H bond dissociations on all surfaces. Then, we find the lowest activation energies for O-H and C-H bond dissociations on Fe(001). We also calculate the activation energies for C-C bond dissociations on Fe(001) and Ni(111) to reveal the selectivity of the catalyst. The comparison among the activation energies for O-H, C-H, and C-C bond dissociations shows the higher selectivity for the ethylene glycol oxidation on Fe(001) than that on Ni(111). Thus, Fe(001) is expected for the highly-active and selective catalytic material of the AFC.

記述言語：日本語  

To clarify the degradation mechanism of lithium-ion battery cathode, we studied the degradation process of the cathode caused by a chemical reaction with ethylene carbonate (EC) via our tight-binding quantum chemical molecular dynamics (TB-QCMD) method. We simulated the dynamics of the chemical reaction of LiCoO_2(010) surface and EC. In addition, our calculated atomic bond population revealed that a Co-O bond of the LiCoO_2(010) surface weakened when an O atom bound with a C atom of EC. This weakening of the Co-O bond indicates that the O atom of the surface is easily removed from the surface and the Co atom is reduced. It is known that the structural change of the cathode after the reduction of the Co atom causes the degradation of the lithium-ion battery cathode. Thus, we suggested that the adsorption of EC resulting in the reduction of Co atoms was the initial process of the degradation of the lithium-ion battery cathode.

記述言語：日本語  

To clarify the degradation mechanism of perfluorosulfonic acid (PFSA) membranes in polymer electrolyte fuel cells, we studied the decomposition process of PFSA side chain by radical species using the first-principles molecular dynamics method. This approach is possible to simulate real-time reactions from a viewpoint of atomic scale and reveal novel reaction pathways that traditional static methods may overlook. We investigated the reactions of OH and H radicals with the side chain model of CF_3CF_2CF_2SO_3H. In the reaction with a OH radical, a water molecule was generated when the OH radical abstracted the hydrogen atom from the side chain. An analysis of the interatomic distances and potential energy profiles revealed that the hydrogen bond between the OH radical and the oxygen atom in the sulfo group lowered the activation energy for the hydrogen abstraction. On the other hand, a H radical reacted with not the hydrogen atom but the oxygen atom in the sulfo group even though the activation energy for the reaction with the oxygen atom is higher than that with the hydrogen atom. This is because the hydrogen atom can escape from the approach of the H radical due to the small radius and mass, while the oxygen atom reacts with the radical due to the large radius and mass relative to the hydrogen atom. Moreover, this result indicates that it is important for clarification of the degradation mechanism to take account of not only statics but also dynamics.

記述言語：日本語  

Sintering of nickel nanoparticles during the long-term operation leads to the degradation of the Ni/YSZ anode. To prevent the sintering, understanding of the sintering process in the Ni/YSZ anode with a porous structure is needed. In this work, to investigate the effect of porosity of the Ni/YSZ anode on the sintering, we modeled the Ni/YSZ multi-nanoparticle models with the porosity of 0.25 and 0.45 and simulated the sintering in the models by using our developed multi-nanoparticle molecular dynamics simulation method that can consider the effects of the properties of the porous structure such as porosity and YSZ nanoparticle framework, etc. It was revealed that the YSZ framework prevented the sintering of nickel nanoparticles in the small pore of the YSZ framework. Furthermore, it was found that the degree of sintering of nickel nanoparticles in the Ni/YSZ model with the porosity of 0.25 is smaller than that of 0.45, because the decrease in the porosity leads to the decrease in the pore size of the YSZ framework. Thus, we suggest that decreasing the porosity of Ni/YSZ anode can inhibit the sintering of nickel nanoparticles.

記述言語：日本語  

記述言語：日本語  

To clarify the degradation mechanism of proton exchange membrane (PEM) in a polymer electrolyte fuel cell (PEFC), we studied the degradation process of Nafion widely used as PEM by the first-principles molecular dynamics (FPMD) method. FPMD calculations were carried out using our "Violet" program, based on density functional theory (DFT) with B3LYP exchange-correlation functional and 6-31G (d) basis sets. We successfully clarified the dynamics of the reactions in which the main chain end was decomposed by OH radicals. Moreover, it was revealed that the reaction pass differs whether there are water molecules or not in the reaction system. In order to elucidate the difference, we calculated activation energies in these reactions by DFT method. The activation energy of the reaction with water molecules is lower than that of without a water molecule. Therefore, we conclude that water molecules work as a catalyst in the degradation reaction.

記述言語：日本語  

In this paper, we discuss the fracture properties of gadolinia doped ceria (GDC) electrolytes for solid oxide fuel cell (SOFC), based on molecular dynamics (MD) simulation and density functional theory (DFT). The ceria based materials like a GDC are expected as electrolytes to lower the operating temperature, however, the short lifetime of GDC prevents their wide applications. Therefore, we executed the tensile test using the MD simulation and DFT calculation and obtained the Young's modulus and the fracture stress of the GDC. Both indicate phase transition where the oxygen coordination number of Ce^<4+> ions changes from eight to six after the yield point. Furthermore, we calculated the Young's modulus and the fracture stress as functions of oxygen concentration. This result shows that the Young's modulus decreases linearly when the oxygen concentration increases, while the fracture stress is insensitive to the changes. This tendency is in good agreement with experimental data qualitatively. We also discuss the effect of steam condition on the fracture properties of GDC, and find the crack advance of GDC is accelerated by the chemical reaction with H_2O molecules.

記述言語：日本語  

The dopant effects on the sintering process of nickel nanoparticles in the nickel and doped zirconia cermet anode were investigated by using molecular dynamics (MD) simulation. In this study, we unraveled the differences of the sintering process, the surface area of the nickel nanoparticles, and the triple phase boundary (TPB) length between the Ni/YSZ and the Ni/ScSZ systems. According to the simulation results, we observed that the extent of sintering in the Ni/YSZ is larger than that in the Ni/ScSZ due to the dopant effect. These observations revealed that the sintering on the YSZ surface takes place more easily than that on the ScSZ surface. Then, the mechanism of the dopant effect on the sintering of nickel nanoparticles is investigated by using density functional theory (DFT). It was found that the low adsorption energy between the nickel and the doped zirconia decreases the movement of the nickel nanoparticles and inhibits the sintering of the nickel nanoparticles on the doped zirconia surface.

記述言語：日本語  

In this study, to elucidate highly-selective catalyst materials for an oxidation reaction of an ethylene glycol (HOCH_2CH_2OH) to an oxalic acid ((COOH)_2), we performed high-speed screening of effective metal catalyst for partial oxidation of HOCH_2CH_2OH via first-principles calculations. Here, to screen effective element for the partial oxidation process, we investigated the oxidation reactivity of the ethylene glycol on the Fe(001), Ni(111), Co(0001), Cu(111), and Pt(111) surfaces. Fe, Ni, and Co are found to be effective for the dissociations of O-H and C-H bonds of HOCH_2CH_2OH, which are elementary reactions process of the above partial oxidation. In addition, the dissociation of the C-H bond is found to require the step structure on the metal catalyst surface. Furthermore, we revealed that Pt completely oxidizes an ethylene glycol to a carbon dioxide since the C-C bond is broken by Pt at the oxidation process. Therefore, we suggest that highly-selective catalyst materials for the partial oxidation of the ethylene glycol consist of Fe, Ni, and Co.

記述言語：日本語  

種別：大会・シンポジウム等 

種別：大会・シンポジウム等 

種別：大会・シンポジウム等 

種別：大会・シンポジウム等 

種別：学会・研究会等 

種別：大会・シンポジウム等 

種別：大会・シンポジウム等