**************** The 16th., Lab Seminar *****************

Date: Thu, December 4, 2003  PM 4:00-

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

Speaker: Yuuki Ohishi

Title: Rotational dynamics of an NH4+ ion in water

Abstract: 
 The structural, thermodynamic, and dynamical properties of a single
ammonium ion in liquid water were investigated using molecular dynamic
simulation techniques. Many-body polarizable model potentials were employed
to describe the molecular interactions. The water molecules were found to
form well-defined hydration shells with a preferred orientation around the
ammonium ion as expected. It was also found that the average water dipole
moment is enhanced in the first hydration shell. The translational and
rotational motion of ammonium ion was examined via the velocity,
angular-momentum, and reorientation-autocorrelation functions. The computed
rotational diffusion coefficients of the ammonium ion in water, which were
determined from the angular momentum autocorrelation function and the
angular mean-square displacement, are in good agreement with the
experimental nuclear magnetic resonance value.

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