Natural Bond Orbitals and the Nature of the Hydrogen Bond.

The charge-transfer component of the energy of interaction between molecules has been a controversial issue for many years. In particular, the values reported from the use of the natural bond orbital analysis of Weinhold and his co-workers are several times larger than those obtained by other methods. I argue that these values are heavily contaminated with basis-set superposition error and are meaningless in the context of intermolecular interactions.