A Molecular Dynamics Simulation of the Structure of Sodium Ion in Liquid Ammonia

The structural properties of Na1/ammonia solution have been studied by means of a molecular dynamics simulation, the experimental density of pure liquid ammonia being used. In contrast to the previous study for the lithium ion in liquid ammonia, a free orientation of the ammonia molecules in the first solvation shell of the sodium ion has been found. The effects of elevated temperature on the structure function of the cationic solvation shell could be observed clearly i.e., an increase in temperature leads to significant changes in molecular orientation and an increase in the average dipole moment of solvated ammonia. The intramolecular geometry changes of an ammonia molecule relative to the pure liquid were similar to those reported for Li1/ammonia solution.