Intermolecular potential for acetonitrile based on ab initio calculations

Abstract

A potential function describing the interaction between two acetonitrile molecules in terms of electrostatic, repulsion, induction and dispersion contributions was constructed using ab initio calculations of molecular properties and IMPT. The minimum energy structure has C_2h symmetry, with the two molecules antiparallel, their centres of mass separated by 3.5 Å, and the CH bonds in the symmetry plane oriented towards the nitrogen atom of the other molecule. Molecular dynamics simulations carried out with the new potential (many-body effects are included via the induction term) predict that liquid acetonitrile possesses only short range structure, there being no correlation between the orientations of molecules separated by more than 5.2 Å. The induced dipole moment in the liquid is almost parallel to the molecular axis, and its magnitude is about 20% of the calculated dipole moment of the isolated molecule.