RESEARCH

Chemical processes taking place in the liquid phase have been of great interest in many aspects in chemistry including organic reactions and the stability of biomolecules. However, the theoretical description of the phenomena is far from complete, especially, in the molecular level. The difficulty lies in the coupling of complicated intramolecular process including the electronic structure and the many body nature of the liquid state, each of which by itself is a non-trivial theoretical problem. Particulary, the description of chemical specificity exhibited in molecualr liquids, represented by the hydrogen-bonding in water, was the main obstacle faced by the liquid state theory. The major break through toward the liquid state theory in chemistry has been made by D. Chandler and H.C. Andersen in 1972 with their theory for the reference interaction site model (RISM).[D. Chandler and H. C. Andersen, J. Chem. Phys., 57, 1930 (1972)] The theory is a natural extension of the Ornstein-Zernike equation of simple liquids to a mixture of atoms but with strong intramolecular correlation which represents chemical bonds. The theory takes account for one of the two important chemical aspects of molecules, geometry, in terms of the site-site interactions between atoms. However, it does not handle the other chemical aspect of molecules, electrostatics, in its original forms.

The charge distribution in a molecule, which is a classical manifestation of the electronic structure, plays a dominant role in determining the chemical specificity of the molecule. Therefore, without including the charge distribution in molecules, the description is incomplete in terms of chemical specificity. A complete chemical characterization of molecular liquids became possible in 1981 due to the appearence of the extended RISM theory which takes the charge distribution as well as the molecular geometry into account.[F. Hirata and P. J. Rossky, Chem. Phys. Lett., 83, 329 (1981)] Applications of the theory to a variety of liquids and solutions have demonstrated its capability of describing the chemical specificity, such as hydrogen-bonding, of liquids in a molecular detail.[F. Hirata, Kikan Kagaku Sosetsu No.26, Molecular Picture of Solution, (in Japanese), pp. 148 (1995)]

Our current research interests and activities are concentrated upon three important problems in the chemical physics, in each of which the extended RISM theory plays a key role:

1. the electronic structure of a molecule in solution
2. solvation thermodynamics of protein and related molecules
3. characterization of spatial and temporal density fluctuation in molecular liquids

In each of the three problems, we have recently proposed new mthod. The work along the three lines are now in progress.

Institute of Molecular Science has education programs in the graduate courses as a part of the Graduate University of Advanced Studies (Sokendai). The faculties of IMS are appointed jointly as the members of the School of Physical Science in the graduate university.

For the details of the research program in the graduate course, please refer to the webpage of SOKENDAI.