********************* The 5th., Lab Seminar **********************

Date: Thu, July 3, 2003  PM 4:00-

Place: No.616 Seminar room
　　　　　　 Graduate School of Information Science

Speaker: Yuuki Ohishi　　

Title: Geometry optimization of molecules in aqueous solution: Joint use
     　 of the mean field approximation and the free-energy gradient method

Abstract:  The average solvent electrostatic potential/molecular dynamics
　　　  (ASEP/MD)calculated by Quantum Mechanics/ Molecular Mechanics
        method (QM/MM) that makes use of the MFA and the free-energy
        gradient method (FEG) are applied together with the multidimensional
        geometry optimization of molecules in solution. The systems studied
        were formamide in aqueous solution and water and methamol in liquid
        phase. The solute molecules ware described through ab initio quantum
        mechanics method (density functional theory or Moller-plesset second
        order perturbation theory) while the solvent structure was obtained
        from Molecular Dynamics calculations. Its main advantage is that it
        permits reducing the number of quantum calculations without
        introducing significant errors either in the energy or the molecular
        properties. It is interesting to note that the influence that the
        basis set or the level of calculation has on the geometry is larger
        than the solvent influence.The solvent,however, induced large
        changes in the solute charge distribution,which became strongly
        polarization, and the solute polarization was accompanied by an
        increase in the solvent structure around the solute.


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