凝縮系のプロトン移動と化学反応に関する量子分子動力学研究

早大学位記番号:新7845早稲田大

ANALISIS TEORI ENERGI DESOLVASI ION NATRIUM PADA PELARUT ELEKTROLIT ORGANIK MENGGUNAKAN DENSITY FUNCTIONAL TIGHT BINDING (DFTB): THEORETICAL ANALYSIS OF DESOLVATION ENERGY SODIUM IONS IN ORGANIC ELECTROLYTE SOLVENTS USING DENSITY FUNCTIONAL TIGHT BINDING (DFTB)

Larutan elektrolit sangat berperan penting sebagai media transfer ion pada baterai. Transfer ion pada antar muka elektrolit dan elektroda dapat menentukan energi desolvasi dan konduktivitas ion. Tujuan penilitian ini adalah untuk mengetahui pengaruh variasi pelarut organik terhadap energi desolvasi lepasnya pelarut organik.  Penelitian ini menggunakan lima pelarut elektrolit organik yaitu Adiponitrile (APN), Acetonitrile (ATN), Butylene Carbonate (BC), Diethyl Carbonate (DEC), dan 1,4-Dioxa­ne (DIO). Parameter yang diamati adalah energi desolvasi menggunakan metode DFTB dengan program Dcdftbmd. Hasil analisis data twoway ANOVA diperoleh signifikansi kurang dari 0,05 dan Ha diterima yang berarti bahwa ada perbedaan yang nyata pada jenis pelarut elektrolit organik terhadap energi desolvasi. Untuk uji lanjut Post Hoc diperoleh bahwa terdapat perbedaan secara signifikan. Berdasarkan parameter yang diamati, dapat disimpulkan bahwa kelima jenis pelarut elektrolit organik memiliki pengaruh terhadap energi desolvasi. Energi desolvasi masing-masing pelarut organik cenderung meningkat seiring dengan semakin banyaknya pelarut organik yang lepas ikatannya dengan Natrium.   ABSTRACT Electrolyte is very important as an ion transfer medium in battery. Ion transfer at the interface between electrolyte and electrode can determine desolvation energy and ion conductivity. The aims of this study is to determine the effect of variations in organic solvent on desolvation energy of organic solvent. In this study, we were used five organic electrolyte solvents namely Adiponitrile (APN), Acetonitrile (ATN), Butylene Carbonate (BC), Diethyl Carbonate (DEC), and 1,4-Dioxa­ne (DIO). The parameter observed were desolvation energy using DFTB method with the Dcdftbmd program. The result of two way ANOVA data analysis obtained a significance of less than 0.05 and Ha was accepted, which means that there is significant difference between the type of organic electrolyte solvent and the desolvation energy. For the Post Hoc test, it was found that there was a significant difference. Based parameter observed, the five organic solvents have an influence on the desolvation energy. Each desolvation energy of organic solvents tends to increase along with the increasing number of organic solvents released of bond with Sodium

Rigorous p<i>K</i>_a Estimation of Amine Species Using Density-Functional Tight-Binding-Based Metadynamics Simulations

Predicting p<i>K</i>_a values for different types of amine species with high accuracy and efficiency is of critical importance for the design of high performance and economical solvents in carbon capture and storage with aqueous amine solutions. In this study, we demonstrate that density-functional tight-binding-based metadynamics simulations are a promising approach to calculate the free energy difference between the protonated and neutral states of amines in aqueous solution with inexpensive computational cost. The calculated p<i>K</i>_a values were in satisfactory agreement with the experimental values, the mean absolute deviation being only 0.09 p<i>K</i>_a units for 34 amines commonly used in CO₂ scrubbing. Such superior reproducibility and correlation compared to estimations by static quantum mechanical calculations highlight the significant effect of dynamical proton transfer processes in explicit solvent molecules for the improvement of the estimation accuracy

Divide-and-Conquer-Type Density-Functional Tight-Binding Simulations of Hydroxide Ion Diffusion in Bulk Water

The diffusion of the hydroxide ion in bulk water was examined by linear-scaling divide-and-conquer density-functional tight-binding molecular dynamics (DC-DFTB-MD) simulations using three different-sized unit cells that contained 522, 1050, and 4999 water molecules as well as one hydroxide ion. The repulsive potential for the oxygen–oxygen pair was improved by iterative Boltzmann inversion, which adjusted the radial distribution function of DFTB-MD simulations to that of the reference density functional theory-MD one. The calculated diffusion coefficients and the Arrhenius diffusion barrier were in good agreement with experimental results. The results of the hydroxide ion coordination number distribution and potential of mean force analyses supported a dynamical hypercoordination diffusion mechanism

Effects of fused thiophene Π-bridge on the electronic and optical properties of modified theaflavin natural dye

Natural dye sensitizers are substances that are sensitive to light colour and can be classified into several classes based on their chemical structure. Theaflavin pigments are unexplored natural dyes used as light sensitizers derived from black tea waste. However, the efficiency of natural dye-sensitized solar cells (DSSC) is lower than that of synthetic ones. To increase the efficiency, an amine donor molecule, a thiophene bridge, and a cyanoacrylic acid anchoring group were added. This improvement was achieved by comparing the LHE values, absorption shifts towards the red spectrum, and electronic parameters before and after modification of the theaflavin structure. This study aimed to analyze the effect of a fused thiophene bridge on the colour pigment of theaflavin on the electronic and optical properties of DSSC. TDDFT was employed with the hybrid functional B3LYP and def2-SVP. The calculated results concluded that adding fused thiophene can shift the wavelength with a maximum value of 256 nm and an increase in LHE of 40%. The addition of five thiophenes can shift the absorption wavelength closer to the red spectrum and satisfy the electronic properties of the DSSC, and the number of electron donor and acceptor sites obeying the law of conservation of charge.</p

Confined water-mediated high proton conduction in hydrophobic channel of a synthetic nanotube

ナノサイズの空間に閉じ込められた水が示す不思議な性質を実証 --高速で水素イオンを運ぶ水の状態を解明--. 京都大学プレスリリース. 2020-02-18.Water confined within one-dimensional (1D) hydrophobic nanochannels has attracted significant interest due to its unusual structure and dynamic properties. As a representative system, water-filled carbon nanotubes (CNTs) are generally studied, but direct observation of the crystal structure and proton transport is difficult for CNTs due to their poor crystallinity and high electron conduction. Here, we report the direct observation of a unique water-cluster structure and high proton conduction realized in a metal-organic nanotube, [Pt(dach)(bpy)Br]4(SO4)4·32H2O (dach: (1R, 2R)-(–)-1, 2-diaminocyclohexane; bpy: 4, 4’-bipyridine). In the crystalline state, a hydrogen-bonded ice nanotube composed of water tetramers and octamers is found within the hydrophobic nanochannel. Single-crystal impedance measurements along the channel direction reveal a high proton conduction of 10−2 Scm−1. Moreover, fast proton diffusion and continuous liquid-to-solid transition are confirmed using solid-state 1H-NMR measurements. Our study provides valuable insight into the structural and dynamical properties of confined water within 1D hydrophobic nanochannels