Hydrogen binding and dissociation in MgScH_n clusters (n ≤ 20)

摘要

Transition metal doped magnesium hydride solids are a leading candidate for hydrogen storage materials. In this investigation, MgScHn clusters (n = 1-20) are theoretically studied using density functional theory and Moller-Plesset perturbation theory. It is determined that hydrogen binds successively to the MgSc diatomic metal center up to MgScH13 when the cluster becomes saturated at 15.9% hydrogen by mass. In contrast to earlier predictions, we shown that for MgScH14 and larger clusters molecular hydrogen dissociates from the core cluster structure. A local minimum is observed on the potential energy surface for larger clusters where dissociated hydrogen interacts with a negatively charged hydride of the core cluster in a dipole-induced dipole intermolecular force, providing insight into the dissociation pathway in bulk magnesium hydride materials doped with transition metals. Analysis of the frontier orbitals and natural bonding analysis of these clusters support this logical dissociation pathway. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.