Reaction Paths, Transition States and Catalysis in Li$_{4}$BN$_{3}$H$_{10}$ from First Principles

Thermodynamic analyses of the complex hydride Li$_{4}$BN$_{3}$H$_{10}$ ($>$10 wt.\% H$_{2}$) predicted favorable hydrogen desorption reactions in the solid, whereas experiments found temperatures above melting were needed before appreciable H$_{2}$ desorption was observed, and the material released NH$_{3}$ at approximately the same temperature. More recent experimental studies successfully catalyzed H$_{2}$ desorption using CoCl$_{2}$ and NiCl$_{2}$, decreasing the H$_{2}$ release temperature. To elucidate the catalytic and decomposition mechanisms that resulted in the measured changes, we have applied \textit{Ab Initio} Molecular Dynamics and Transition State Theory methods to find reaction pathways and determine the rate limiting steps in pristine and catalyzed Li$_{4}$BN$_{3}$H$_{10}$. We observed the formation of several important reaction intermediates, as well as free H$_{2}$ and NH$_{3}$ in the bulk liquid. Finally, We studied the formation of vacancies and interstitials that are promising candidates for rate-limiting steps in the desorption reactions and determined energy barriers for each reaction step.