2018 Fiscal Year Final Research Report

Spatial-Decomposition Analysis of Transport Coefficients

Research Project

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Project/Area Number	15K13550
Research Category	Grant-in-Aid for Challenging Exploratory Research
Allocation Type	Multi-year Fund
Research Field	Biological physics/Chemical physics/Soft matter physics
Research Institution	Osaka University
Principal Investigator	Matubayasi Nobuyuki 大阪大学, 基礎工学研究科, 教授 (20281107)
Co-Investigator(Kenkyū-buntansha)	石塚良介大阪大学, 基礎工学研究科, 助教 (30462196)
Project Period (FY)	2015-04-01 – 2019-03-31
Keywords	輸送係数 / 時間相関関数 / 空間分割 / 電気伝導度 / Green-Kubo式 / 分子シミュレーション / 粘度 / 緩和弾性率
Outline of Final Research Achievements	Spatial decomposition was performed for the electrical conductivity. The time correlation function of electric current conditioned by the ion-ion distance was defined, and the conductivity was expressed as a space-time integral of a spatially-decomposed time correlation function. The analysis scheme was applied to ionic liquids, and it was found that the ion-ion correlation over nm scale affects the conductivity. The spatial-decomposition formula was further developed for the viscosity, the relaxation modulus, the response of the orientational correlation time of a solvent molecule upon addition of a solute molecule, and the solvation free energy. The contributions to these properties from the solvent molecules at a variety of distances from the solute were addressed quantitatively, and a systematic approach was established to elucidate the effects of spatial correlations among the solute and solvent molecules on transport, spectroscopic, and thermodynamics properties.
Free Research Field	物理化学
Academic Significance and Societal Importance of the Research Achievements	電解液は電池開発の基本要素の1つであり、その物性を規定する輸送係数が電気伝導度である。時間相関関数によって表現される輸送係数の解析に、直感にアピールするイオン対のような空間的描像を取り入れることを本研究の目的とした。時間的描像と空間的描像を統合した空間分割表式を開発し、次世代電解液として期待されるイオン液体の伝導度に対してイオン間相関の影響が及ぶ空間範囲を解析した。また、粘度、緩和弾性率、溶媒和自由エネルギーといった様々な物理量に対する空間分割表式も定式化し、これまでに空間情報に基づく議論が難しった輸送係数、分光測定量、熱力学量を距離相関の立場から系統的に解析する手法を確立した。