Molecular dynamics simulations of the aqueous solution of tetramethylammonium chloride

A molecular dynamics simulation of 0.555 molal tetramethylammonium chloride in aqueous solution as been performed at 293 K. The tetramethylammonium cations (TMA) are treated as charged ‘pseudo-atoms’ and a flexible 3-site model employed for the water molecules. Structural properties of the system are discussed on the basis of radial distribution functions, orientation of he molecules inn the hydration shells of the ions and their geometrical arrangement. The power spectra and average number of H-bonds of a water molecule in the hydration shells of the ions and in bulk solvent were computed. The TMA exhibits ‘apolar’ and ‘ionic’ properties and itss influence on the structure of bulk water is minor. Association of ions occurs even for moderate concentration and solvent-separated ion pairs are formed.