Modeling and stabilities of Mg/MgH2 interfaces: A first-principles investigation

Abstract

We have theoretically investigated the modeling and the structural stabilities of various Mg/MgH2 interfaces, i.e. Mg($10\bar 10$101¯0)/MgH2(210), Mg(0001)/MgH2(101) and Mg($10\bar 10$101¯0)/MgH2(101), and provided illuminating insights into Mg/MgH2 interface. Specifically, the main factors, which impact the interfacial energies, are fully considered, including surface energies of two phases, mutual lattice constants of interface model, and relative position of two phases. The surface energies of Mg and MgH2, on the one hand, are found to be greatly impacting the interfacial energies, reflected by the lowest interfacial energy of Mg(0001)/MgH2(101) which is comprised of two lowest energy surfaces. On the other hand, it is demonstrated that the mutual lattice constants and the relative position of two phases lead to variations of interfacial energies, thus influencing the interface stabilities dramatically. Moreover, the Mg-H bonding at interface is found to be the determinant of Mg/MgH2 interface stability. Lastly, interfacial and strain effects on defect formations are also studied, both of which are highly facilitating the defect formations. Our results provide a detailed insight into Mg/MgH2 interface structures and the corresponding stabilities.

Nanostructured Metal Hydrides for Hydrogen Storage

“…In addition to surface energies, the energy of internal interfaces and grain boundaries can contribute meaningfully to the thermodynamics of metal hydride NPs, particularly when phases coexist during (de)­hydrogenation. Interface energies can be computed by explicitly attaching two phases within periodic boundary conditions in DFT − or by using appropriately parametrized classical force fields. However, because determining lattice commensurability and preferred interface orientation can be difficult, this approach is best suited for simpler intermetallic and binary hydrides.…”

First-principles investigation of the effects of Ni and Y co-doped on destabilized MgH2

“…Metal hydrides with a high hydrogen storage capacity and demonstrated cycling capability, [1][2][3][4] are considered to be some of the most promising hydrogen storage media for automotive applications. Among these hydrogen storage materials, magnesium hydride (MgH 2 ) has been investigated extensively in the last two decades due to its high hydrogen storage capacity of 7.6 wt% and good reversibility, [5][6][7] together with the cheap cost and light weight of magnesium.…”

Understanding the Decomposition Mechanisms of LiNH2, Mg(NH2)2, and NaNH2: A Joint Experimental and Theoretical Study

“…Second, the adoption of various metal amide surfaces involves choice of surface miller index and surface termination, which could be difficult due to the current shortage of a systematic theoretical study on surface stabilities of these amides. We have found that the surface stabilities and terminations have a great influence on the surface or interfaces properties in the systems of Mg, , Mg/MgH 2 , and CeH 2.73 /CeO 2 . Considering that the main goal of our study is to locate the commons in and differences between these metal amides, we choose bulk calculations as our main measure to investigate the mechanism of these metal amide decompositions.…”