First-principles density functional studies of high-performance hydrogen storage materials

Hydrogen-fueled vehicles require a cost-effective, light-weight material that stores hydrogen at a high (volumetric and gravimetric) density, and binds hydrogen strongly enough to be stable, but weakly enough that the H2 can be easily liberated with minimal heat input at ambient pressures and temperatures. Recent research efforts have been focused on new multicomponent storage systems involving multiple compounds on both sides of the reaction. Predicting crystal structures of new solid-state hydrides and determining favored reaction pathways in multinary hydride systems are two of the most important challenges to theory. Using Li-Mg-N-H and Li-Mg-B-N-H as examples, we will demonstrate how first-principles calculations can be used to determine phase diagrams and hydrogenation reactions in multicomponent systems entirely from first principles. We will also review our efforts in the development of theoretical methods for determining crystal structures of new, yet-unsynthesized materials. Accurate theoretical predictions of hydrogenation enthalpies in alanates, borohydrides, and amides have been obtained without any experimental input. This research has been supported by DOE grants DE-FC36-04GO14013 and DE-FG02-05ER46253.