Hydrogen bond
Hydrogen bonds can be intermolecular (occurring between separate molecules) or intramolecular (occurring among parts of the same molecule). Depending on the nature of the donor and acceptor atoms which constitute the bond, their geometry, and environment, the energy of a hydrogen bond can vary between 1 and 40 kcal/mol. This makes them somewhat stronger than a van der Waals interaction, and weaker than fully covalent or ionic bonds. This type of bond can occur in inorganic molecules such as water and in organic molecules like DNA and proteins.
Iron–hydrogen alloy
The hydrogen in typical iron hydrides may contribute up to 13 ppm in its weight. Varying the amount of hydrogen, as well as controlling its chemical and physical makeup in the final iron hydride (either as a solute element, or as a precipitated phase), hastens the movement of those dislocations that make pure iron ductile, and thus controls and undermines its qualities. Varying the other alloying elements and controlling their chemical and physical makeup also controls, but enhances its qualities. These qualities include such things as the hardness, quenching behaviour, need for annealing, tempering behaviour, yield strength, and tensile strength of the resulting iron-hydrogen alloy. The retension of iron hydride's strength compared to pure iron is possible only by maintaining iron's ductility.