Charge Density Methods in Hydrogen Bond Studies

The history of hydrogen bonding is briefly outlined and the current descriptive elements used in the understanding and the study of hydrogen bonds are summarized. The specific challenges that emerge when making experimental charge density studies of hydrogen bonded systems are explained and a number of recent and important charge density studies have been selected to illustrate the significant impact that the experimental charge density modeling continues to have on the understanding of the nature of the hydrogen bonding, both in the electrostatic, longer hydrogen bonds and in the very short, strong hydrogen bonds.