Abstract
Because of the slow convergence of static electricity, a molecular dynamic simulated system for charged particles is difficult to handle. If we force to use the truncation radius, the calculation of forces will generate considerable errors. However, by using Ewald sum which deals with static electricity, we are entitled to get reasonable results. But, Ewald sum formula is too complex to use. The force should be gotten first, so the correct address type can be applied in molecular dynamic simulation.The research can be divided into three parts:I. Get the right formula by derived Ewald sum, then verify if the Ewald sumprogram process is correct or not.II. Apply the formula into molecular dynamics simulation - the established watersystem.III. Establish salt solution.Finally, the research is discussing about the effect of hydrogen bonds between water molecules and ions in different concentrations. The result shows that the destruction of hydrogen bonds between water molecules and ions is proportional to hydration.