Nonempirical quantification of molecular interactions in supramolecular assemblies.

A new nonempirical scheme for the computation of realistic atomic charges from the sole knowledge of molecular or crystalline structures and of two ab initio parameters per chemical element (a configuration energy and the radius of the most diffuse valence orbital) is presented. Charge distributions obtained from this formalism are consistent with common chemical knowledge and found to be in agreement with available X-ray diffraction studies. They are also compatible with electrical-field gradients derived from solid-state NMR measurements. It is also shown how the total electrostatic energy associated with each charge distribution may be used to quantify van der Waals as well as hydrogen bond interactions from an energetic point of view. Finally, the position of the new formalism relative to other ab initio schemes is discussed both qualitatively and quantitatively.