Thesis (M.Sc.)--Chulalongkorn University, 1995

The solution of one K+ in 215 ammonia, one I- in 215 ammonia and one KI in 214 ammonia have been investigated by Molecular Dynamics simulation at an average temperature of 240 K, using flexible ammonia model. The K+ -ammonia, I--ammonia and K+-I- pair potentials were newly developed, based on ab initio calculations, in which the basis set superposition error (BSSE) was corrected. The structural properties of the solution are described in terms of radial distribution functions (RDFs) and running integration numbers. The coordination numbers of K+ of 8.7 and 8.9 were found for the K+-ammonia and the K+-I--ammonia systems, respectively. The corresponding values of I- are 15.9 and 15.1 for the I--ammonia and the K+-I--ammonia systems. The presence of the counter ion causes the shift of the solvation radius of the K+ of 0.2 Aํ to the shorter distance, the reorientation of its first shell molecules, the split of the second peak of the K+-N RDF and so on. The dynamical properties of the solution, which are investigated in terms of autocorrelation functions and their Fourier transforms are in good agreement with those reported by both theoretical and experimental investigation.