※ 半角英数字
 年 ~ 
検索結果: 178 件中 1件目~20件目を表示


Initialising ...



Initialising ...


Initialising ...


Initialising ...


Initialising ...


Initialising ...


Initialising ...


Initialising ...



Roles of excess minority carrier recombination and chemisorbed O$$_{2}$$ species at SiO$$_{2}$$/Si interfaces in Si dry oxidation; Comparison between p-Si(001) and n-Si(001) surfaces

津田 泰孝; 吉越 章隆; 小川 修一*; 坂本 徹哉*; 山本 善貴*; 山本 幸男*; 高桑 雄二*

Journal of Chemical Physics, 157(23), p.234705_1 - 234705_21, 2022/12

 被引用回数:0 パーセンタイル:0.01(Chemistry, Physical)

This paper gives experimental evidence for that (1) the excess minority carrier recombination at the SiO$$_2$$/p-Si(001) and SiO$$_2$$/n-Si(001) interfaces is associated with the O$$_2$$ dissociative adsorption, (2) the 700-eV X-ray induced enhancement of the SiO$$_2$$ growth is not caused by the band flattening due to the surface photovoltaic effect but ascribed to the electron-hole pair creation due to core level photoexcitation for the spillover of the bulk Si electronic states to the SiO$$_2$$ layer, (3) changes of band bending result from the excess minority carrier recombination at the oxidation-induced vacancy site when turning on and off the X-ray irradiation, and (4) a metastable chemisorbed O$$_2$$ species (Pb1-paul) plays a decisive role in combining two kinds of the reaction loops of single- and double-step oxidation. Based on the experimental results, the unified Si oxidation reaction model mediated by point defect generation [Jpn. J. Appl. Phys. 59, SM0801 (2020)] is extended from a viewpoint of (a) the excess minority carrier recombination at the oxidation-induced vacancy site and (b) the trapping-mediated adsorption through the chemisorbed O$$_2$$ species at the SiO$$_2$$/Si interface.


X-ray absorption spectra of aqueous cellobiose; Experiment and theory

赤沢 第輔; 佐々木 岳彦*; 長坂 将成*; 志賀 基之

Journal of Chemical Physics, 156(4), p.044202_1 - 044202_7, 2022/01

 被引用回数:1 パーセンタイル:0.01(Chemistry, Physical)

セルロースの水和構造は、分子レベルでのバイオマスセルロースの加水分解メカニズムの理解のために非常に重要である。本論文では、セルロースの2糖の単量体であるセロビオースの水溶液について、そのX線吸収分光法(XAS)スペクトルの測定と理論計算を組み合わせた研究について報告する。測定に関する項目では高解像度の炭素K端のXASスペクトルの測定について報告する。理論計算の項目では、第一原理分子動力学計算と励起状態計算を用いてXASのシミュレーションを求める手法と結果ついて論ずる。セロビオースのXASには289.3eV, 290.7eV, 293.6eVの3つのピークがあり、それぞれアルコール基,ヘミアセタール基,アルコール及びヘミアセタール基の両方に対応することがわかった。さらに、25$$^{circ}$$Cから60$$^{circ}$$Cまでの温度変化に対してスペクトルの高さが規則的に変化し、それがセロビオースと水分子の水素結合の数の変化を表していることがわかった。このスペクトルの変化は様々な環境におけるセルロースの水和構造を知るための情報として有用であると考えられる。


${it Ab initio}$ study of nuclear quantum effects on sub- and supercritical water

Thomsen, B.; 志賀 基之

Journal of Chemical Physics, 155(19), p.194107_1 - 194107_11, 2021/11

 被引用回数:4 パーセンタイル:60.18(Chemistry, Physical)

The structures of water in the ambient, sub-, and supercritical conditions at various densities were studied systematically by ${it ab initio}$ path integral molecular dynamics simulations. It was found that the nuclear quantum effects (NQEs) have significant impact on the structure of hydrogen bonds in close contact, not only in the ambient condition but also in the sub-, and supercritical conditions. The NQEs on the structure beyond the hydrogen bond contact are important in ambient water, but not much for water in the sub-, and supercritical conditions. The NQEs are furthermore important for determining the number of hydrogen bonds in the ambient conditions, this role is however diminished in the sub- and supercritical conditions. The NQEs does nevertheless show their importance in determining the intramolecular structure of water and the close contact structures of the hydrogen bonds, even at sub- and supercritical conditions. Using the RPBE-D3 functional, the computed radial distribution functions for the ambient water are in excellent agreement with experimental data, upgrading our previous results using the BLYP-D2 functional [Machida, et al., J. Chem. Phys. 148, 102324 (2018)]. The computed radial distribution functions for water in the sub- and supercritical conditions were carefully compared with experiment. In particular, we found that the first peak in hydrogen pair distribution functions matches only when the NQEs are taken into account.


Self-learning hybrid Monte Carlo method for isothermal-isobaric ensemble; Application to liquid silica

小林 恵太; 永井 佑紀; 板倉 充洋; 志賀 基之

Journal of Chemical Physics, 155(3), p.034106_1 - 034106_9, 2021/07

 被引用回数:2 パーセンタイル:34.19(Chemistry, Physical)



Nuclear quantum effects on autoionization of water isotopologs studied by ${it ab initio}$ path integral molecular dynamics

Thomsen, B.; 志賀 基之

Journal of Chemical Physics, 154(8), p.084117_1 - 084117_10, 2021/02

 被引用回数:4 パーセンタイル:60.18(Chemistry, Physical)



Quantum-mechanical hydration plays critical role in the stability of firefly oxyluciferin isomers; State-of-the-art calculations of the excited states

野口 良史*; 樋山 みやび*; 志賀 基之; 秋山 英文*; 杉野 修*

Journal of Chemical Physics, 153(20), p.201103_1 - 201103_6, 2020/11

 被引用回数:2 パーセンタイル:17.23(Chemistry, Physical)



Structure refinement of black phosphorus under high pressure

赤浜 裕一*; 宮川 仁*; 谷口 尚*; 佐野 亜沙美; 町田 真一*; 服部 高典

Journal of Chemical Physics, 153(1), p.014704_1 - 014704_5, 2020/07

 被引用回数:5 パーセンタイル:45.64(Chemistry, Physical)

室温下で3.2GPaまでの圧力における黒リンの構造解析を粉末中性子回折によって行った。高圧下のリン原子の結合距離と結合角を精密に決め、これまでのX線単結晶解析の結果[Brown and Randqvist, Acta Cryst. 19, 684 (1965)]と一致することを確認した。結晶格子は異方的な圧縮を示すが、P1-P2およびP1-P3結合距離は圧力によらずほぼ一定であり、P3-P1-P2結合角のみ顕著に減少した。この結果から、Cartzら[J. Chem. Phys. 71, 1718 (1979)]により報告されている結合距離との顕著なずれは、解消された。我々の構造データは、高圧下における黒リンのDirac半金属状態を明らかにするに役立つ。


Terahertz and mid-infrared spectroscopy of matrix-isolated clusters and matrix-sublimation ice of D$$_2$$O

山川 紘一郎; 那須 裕一*; 鈴木 菜摘*; 清水 元希*; 荒川 一郎*

Journal of Chemical Physics, 152(17), p.174310_1 - 174310_13, 2020/05

 被引用回数:0 パーセンタイル:0.01(Chemistry, Physical)

超高真空下テラヘルツ・赤外吸収分光装置を開発し、この装置を用いてAr固体中に分離したD$$_2$$Oクラスターの吸収スペクトルを測定した。2, 3, 4量体によるテラヘルツ吸収ピークを帰属するため、スペクトルの温度依存性とD$$_2$$O希釈率依存性を分析した。帰属の妥当性は、ONIOM法を用いた第一原理計算を用いて検証した。これにより、2量体の全ての分子間振動モード、3量体と4量体の赤外吸収強度が大きい分子間振動モードを同定することができた。Ar固体中にD$$_2$$Oクラスターを分離後、Arのみを昇華してD$$_2$$O氷を生成した。昇華温度と希釈率を変えてD$$_2$$O氷を生成し、テラヘルツスペクトルから結晶度を定量的に評価することで、結晶化にはD$$_2$$O単量体の拡散が決定的なプロセスであることを明らかにした。


Changes in electronic structure of carbon supports for Pt catalysts induced by vacancy formation due to Ar$$^{+}$$ irradiation

岡崎 宏之*; 垣谷 健太*; 木全 哲也*; 出崎 亮*; 越川 博*; 松村 大樹; 山本 春也*; 八巻 徹也*

Journal of Chemical Physics, 152(12), p.124708_1 - 124708_5, 2020/03

 被引用回数:2 パーセンタイル:17.23(Chemistry, Physical)

X-ray absorption spectroscopy measurements were performed for the C K-edge of Pt nanoparticles on Ar$$^{+}$$-irradiated carbon supports in order to elucidate the origin of improved catalyst performance after the introduction of vacancies into the carbon support. We observed a change in the electronic structure at the interface between the Pt nanoparticles and the carbon support after vacancy introduction, which is in good agreement with theoretical results. The results indicated that vacancy introduction resulted in a drastic change in the Pt-C interactions, which likely affected the d-band center of the Pt nanoparticles and led to the enhancement of the oxygen reduction reaction in catalysts.


Thermal behavior, structure, dynamic properties of aqueous glycine solutions confined in mesoporous silica MCM-41 investigated by X-ray diffraction and quasi-elastic neutron scattering

吉田 亨次*; 井上 拓也*; 鳥越 基克*; 山田 武*; 柴田 薫; 山口 敏男*

Journal of Chemical Physics, 149(12), p.124502_1 - 124502_10, 2018/09

 被引用回数:3 パーセンタイル:15.53(Chemistry, Physical)

異なる幾つかの、グリシン濃度, pH、および充填率(=グリシン溶液の質量/MCM-41の乾燥質量))をパラメーターとして、メソポーラスシリカ(MCM-41)に閉じ込められたグリシン水溶液の示差走査熱量測定、X線回折および準弾性中性子散乱(QENS)を305-180Kの温度範囲で実施して、グリシン水溶液の熱的挙動, 構造、および動的特性に対する閉じ込め効果を検討した。


Neutron scattering studies on short- and long-range layer structures and related dynamics in imidazolium-based ionic liquids

根本 文也*; 古府 麻衣子; 長尾 道弘*; 大石 一城*; 高田 慎一; 鈴木 淳市*; 山田 武*; 柴田 薫; 上木 岳士*; 北沢 侑造*; et al.

Journal of Chemical Physics, 149(5), p.054502_1 - 054502_11, 2018/08

 被引用回数:16 パーセンタイル:69.9(Chemistry, Physical)

Alkyl-methyl-imidazolium ionic liquids C$$n$$mimX ($$n$$: alkyl-carbon number, X: anion) have short-range layer structures consisting of ionic and neutral (alkylchain) domains. To investigate the temperature dependences of the interlayer, interionic group, and inter-alkylchain correlations, we have measured the neutron diffraction (ND) of C$$n$$mimPF$$_6$$ ($$n$$ = 16, 9.5, 8). The quasielastic neutron scattering (QENS) of C16mimPF$$_6$$ was also measured to study the dynamics of each correlation. C16mimPF$$_6$$ shows a first-order transition between the liquid (L) and liquid crystalline (LC) phases at $$T_{rm c}$$ = 394 K. C8mimPF$$_6$$ exhibits a glass transition at $$T_{rm g}$$ = 200 K. C9.5mimPF$$_6$$ has both transitions at $$T_{rm c}$$ = 225 K and $$T_{rm g}$$ = 203 K. In the ND experiments, all samples exhibit three peaks corresponding to the correlations mentioned above. The widths of the interlayer peak at ca. 0.2 $AA$^{-1}$$ changed drastically at the L-LC transitions, while the interionic peaks at ca. 1 $AA$^{-1}$$ exhibited a small jump at $$T_{rm c}$$. The peak position and area of the three peaks did not change much at the transition. The structural changes were minimal at $$T_{rm g}$$. The QENS experiments demonstrated that the relaxation time of the interlayer motion increased tenfold at $$T_{rm c}$$, while those of other motions were monotonous in the whole temperature region. The structural and dynamical changes are characteristic of the L-LC transition in imidazolium-based ionic liquids.


Nuclear quantum effects of light and heavy water studied by all-electron first principles path integral simulations

町田 昌彦; 加藤 孝一郎*; 志賀 基之

Journal of Chemical Physics, 148(10), p.102324_1 - 102324_11, 2018/03


 被引用回数:15 パーセンタイル:69.9(Chemistry, Physical)

水,重水,トリチウム水の液体状態における構造を第一原理経路積分分子動力学法を用いて研究した。用いた計算手法は、電子と原子核のすべてを量子力学的に取り扱うものであり、現時点で最も正確な計算手法の一つである。シミュレーションした結果は、実験とおおよそ一致しており、核量子効果により、同位体間の構造上の違いが明らかにされた。特に特筆すべき結果は、水分子内のOH共有結合中のHが隣接水分子との水素結合上の中点まで移動できる一方、重水素,トリチウムの順に中点まで行ける確率が減少するという傾向を得たことである。しかしながら、実験との完全な一致は未だ得られておらず、密度汎関数法の改良が必須であることが示唆された。また、最近の研究成果である密度汎関数に対するvan der Waals補正は液体状態における同位体効果を研究する上で必須であることが分かった。


Behavior of intermolecular interactions in $$alpha$$-glycine under high pressure

篠崎 彩子*; 小松 一生*; 鍵 裕之*; 藤本 千賀子*; 町田 真一*; 佐野 亜沙美; 服部 高典

Journal of Chemical Physics, 148(4), p.044507_1 - 044507_8, 2017/01

 被引用回数:8 パーセンタイル:44.64(Chemistry, Physical)



Enhancement of SiO$$_{2}$$/Si(001) interfacial oxidation induced by thermal strain during rapid thermal oxidation

小川 修一*; Tang, J.*; 吉越 章隆; 石塚 眞治*; 高桑 雄二*

Journal of Chemical Physics, 145(11), p.114701_1 - 114701_7, 2016/09

 被引用回数:3 パーセンタイル:11.74(Chemistry, Physical)



The Structure of molten CuCl; Reverse Monte Carlo modeling with high-energy X-ray diffraction data and molecular dynamics of a polarizable ion model

Alcaraz, O.*; Trull$`a$s, J.*; 田原 周太*; 川北 至信; 武田 信一*

Journal of Chemical Physics, 145(9), p.094503_1 - 094503_7, 2016/09

 被引用回数:3 パーセンタイル:11.74(Chemistry, Physical)

The results of the structural properties of molten copper chloride are reported from high-energy X-ray diffraction measurements, reverse Monte Carlo modeling method, and molecular dynamics simulations using a polarizable ion model. The simulated X-ray structure factor reproduces all trends observed experimentally, in particular the shoulder at around 1 $AA $^{-1}$$ related to intermediate range ordering, as well as the partial copper-copper correlations from the reverse Monte Carlo modeling, which cannot be reproduced by using a simple rigid ion model. It is shown that the shoulder comes from intermediate range copper-copper correlations caused by the polarized chlorides.


Role of van der Waals corrections in first principles simulations of alkali metal ions in aqueous solutions

池田 隆司; Boero, M.*

Journal of Chemical Physics, 143(19), p.194510_1 - 194510_7, 2015/11

 被引用回数:25 パーセンタイル:75.45(Chemistry, Physical)

最局在ワニエ関数を基にした第一原理ベースのファンデルワールス補正を実装しアルカリ金属イオン水溶液における性能と信頼性を調べた。よく使われているrevPBE GGA汎関数と組み合わせると水分子の構造と動的性質のどちらにも無視できない影響があり、特にアルカリイオンの水和殻に対して顕著な影響があることがわかった。これらの影響はより強い構造形成イオンおよび構造破壊イオンにおいてより明瞭であった。さらに、水分子の拡散係数と再配向相間時間が系統的な変化を示し、長距離分散補正を無視した場合よりも実験結果をよく再現することがわかった。


A Hybrid framework of first principles molecular orbital calculations and a three-dimensional integral equation theory for molecular liquids; Multi-center molecular Ornstein-Zernike self-consistent field approach

城戸 健太朗; 笠原 健人*; 横川 大輔*; 佐藤 啓文*

Journal of Chemical Physics, 143(1), p.014103_1 - 014103_9, 2015/07

 被引用回数:3 パーセンタイル:11.86(Chemistry, Physical)

In this study, we reported the development of a new quantum mechanics/molecular mechanics (QM/MM)-type framework to describe chemical processes in solution by combining standard molecular-orbital calculations with a three-dimensional formalism of integral equation theory for molecular liquids (MC-MOZ method). The theoretical procedure is very similar to the 3D-RISM-SCF approach. Since the MC-MOZ method is highly parallelized for computation, the present approach has the potential to be one of the most efficient procedures to treat chemical processes in solution. Benchmark tests to check the validity of this approach were performed for two solute (solute water and formaldehyde) systems and a simple S$$rm_N$$2 reaction (Cl$$^-$$ + CH$$_3$$Cl $$rightarrow$$ ClCH$$_3$$ + Cl$$^-$$) in aqueous solution. The results for solute molecular properties and solvation structures obtained by the present approach were in reasonable agreement with those obtained by other hybrid frameworks and experiments. In particular, the results of the proposed approach are in excellent agreements with those of 3D-RISM-SCF.


Distinct dissociation kinetics between ion pairs; Solvent-coordinate free-energy landscape analysis

米谷 佳晃

Journal of Chemical Physics, 143(4), p.044506_1 - 044506_9, 2015/07

 被引用回数:15 パーセンタイル:57.28(Chemistry, Physical)

Different ion pairs exhibit different dissociation kinetics: however, while the nature of this process is vital for understanding various molecular systems, the underlying mechanism remains unclear. In this study, to examine the origin of different kinetic rate constants for this process, molecular dynamics simulations were conducted for LiCl, NaCl, KCl, and CsCl in water. The results showed substantial differences in dissociation rate constant. Analysis of the free-energy landscape with a solvent reaction coordinate and subsequent rate component analysis showed that the differences in these rate constants arose predominantly from the variation in solvent-state distribution between the ion pairs. The formation of a water-bridging configuration, in which the water molecule binds to an anion and a cation simultaneously, was identified as a key step in this process: water-bridge formation lowers the related dissociation free-energy barrier, thereby increasing the probability of ion-pair dissociation. Consequently, a higher probability of water-bridge formation leads to a higher ion-pair dissociation rate.


Nitrogen K-edge X-ray absorption near edge structure of pyrimidine-containing nucleotides in aqueous solution

島田 紘行*; 南 寛威*; 奥泉 直人*; 佐久間 一郎*; 鵜飼 正敏*; 藤井 健太郎; 横谷 明徳; 福田 義博*; 斎藤 祐児

Journal of Chemical Physics, 142(17), p.175102_1 - 175102_9, 2015/05


 被引用回数:10 パーセンタイル:41.65(Chemistry, Physical)

X-ray absorption near edge structure (XANES) was measured at energies around the N K-edge of the pyrimidine-containing nucleotides cytidine 5'-monophosphate (CMP), 2'-deoxythymidine 5'-monophosphate (dTMP), and uridine 5'-monophosphate (UMP) in aqueous solutions and in dried films under various pH conditions. The features of resonant excitations below the N K-edge in the XANES spectra for CMP, dTMP, and UMP changed depending on the pH of the solutions. The spectral change thus observed is systematically explained by the chemical shift of the core-levels of N atoms in the nucleobase moieties caused by structural changes due to protonation or deprotonation at different proton concentrations. This interpretation is supported by the results of theoretical calculations using density functional theory for the corresponding nucleobases in the neutral and protonated or deprotonated forms.


Investigation of the influence of coadsorbent dye upon the interfacial structure of dye-sensitized solar cells

本田 充紀; 柳田 真利*; Han, L.*; 宮野 健次郎*

Journal of Chemical Physics, 141(17), p.174709_1 - 174709_7, 2014/11


 被引用回数:8 パーセンタイル:31.83(Chemistry, Physical)

The interface between Ru(tcterpy)(NCS)$$_{3}$$TBA$$_{2}$$ [black dye (BD); tcterpy = 4,4',4''-tricarboxy-2,2':6',2''-terpyridine, TBA = tetrabutylammonium cation] and nanocrystalline TiO$$_{2}$$, as found in dye-sensitized solar cells, is investigated by soft-X-ray synchrotron radiation and compared with the adsorption structure of $$cis$$-Ru(Hdcbpy)$$_{2}$$(NCS)$$_{2}$$TBA$$_{2}$$ (N719; dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) on TiO$$_{2}$$ to elucidate the relationship between the adsorption mode of BD and the photocurrent with and without coadsorbed indoline dye D131. The depth profile is characterized with X-ray photoelectron spectroscopy and S $$K$$-edge X-ray absorption fine structure using synchrotron radiation. Both datasets indicate that one of the isothiocyanate groups of BD interacts with TiO$$_{2}$$ via its S atom when the dye is adsorbed from a single-component solution. In contrast, the interaction is slightly suppressed when D131 is coadsorbed, indicated by the fact that the presence of D131 changes the adsorption mode of BD. Based upon these results, the number of BD dye molecules interacting with the substrate is shown to decrease by 10% when D131 is coadsorbed, and the dissociation is shown to be related to the short-circuit photocurrent in the 600-800 nm region. The design of a procedure to promote the preferential adsorption of D131 therefore leads to an improvement of the short-circuit current and conversion efficiency.

178 件中 1件目~20件目を表示