An intermolecular potential function for Na+-acetonitrile obtained from ab initio calculations.: Application to liquid simulations

An analytical function that describes the interaction between an Na+ cation and an acetonitrile molecule was constructed from ab initio calculations. The interaction energy was calculated at the MP2/6-311 + G* level at 120 points on the potential surface and corrected for the basis set superposition error using the counterpoise method. A modified version of this function was also obtained by including an induction term in order to consider interactions between more than two bodies. The results for the simulations of an Na+ cation in acetonitrile show that the coordination sphere consists of six molecules in an octahedral arrangement. Interaction with neighbouring molecules is quite strong but decreases sharply with the distance; inclusion of the induction effects leads to a more symmetric coordination sphere. (C) 1998 Elsevier Science B.V. All rights reserved.