| 研究実績の概要 |
We investigated structural as well as electronic properties and dynamic features of ionic liquids with the help of fast, state-of-the-art semi-empirical quantum-chemical simulation methods. At the beginning, considerable efforts were undertaken to optimize implementations of existing algorithms to make them applicable to modern parallel computer architecture and enable a fast generation of molecular clusters of ionic liquids with varying constraints. With the help of this algorithm, structures of molecular clusters of ionic liquids consisting of methyl-, ethyl- and butylmethylimmidazolium cations and nitrate anions were generated and prepared for subsequent investigation by quantum-chemical methods. All structures could be successfully optimized using the fragment-molecular-orbital density-functional tight-binding method. After the validity of these structures were verified by comparing to existing simulation studies and experiments, we proceeded to electronic structure calculations. First, we investigated the effect of different alkyl-side chains on the structures of the ionic liquids as well as the effect on the redox properties, especially the HOMO-LUMO gap. On small-sized molecular clusters of ionic liquids, molecular dynamics simulation using the density-functional tight-binding method was performed. To enable more efficient simulations, the extended Lagrangian protocol can be applied to the investigated systems. The results of such calculations provide insight into the structure and dynamics of ionic liquids and a publication on this topic is in preparation.
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