Understanding the hydrogen bond using quantum chemistry

Reformulations of the Hartree-Fock and MP2 equations facilitate the interpretation of quantum mechanical results in terms of familiar chemical concepts, such as inner shell, bond, and lone pair electrons. Quantum mechanical calculations show that the hydrogen bond in the water dimer can be understood as the competition between the attractive interaction potential energy and the repulsive internal electronic kinetic energy of the water molecules. The former term can be approximated by classical electrostatic interactions. An understanding of this hydrogen- bonding model facilitates the analysis of the effect of solvation on amino acids, especially the role played by water molecules on the stabilization of the zwitter- ion form.