First-principles calculation of dehydrogenating properties of MgH2-V systems

Abstract

Based on experimental results in which VH 0.81 /MgH 2 interface was found during the process of mechanically milling MgH 2 +5at%V nanocomposite, a VH/MgH 2 interface is designed and constituted in this work. A first-principles plane-wave pseudopotential method based on Density Functional Theory (DFT) has been used to investigate the vanadium alloying effects on the dehydrogenating properties of magnesium hydride, i.e., MgH 2 . A low absolute value of the negative heat of formation of VH/MgH 2 interface compared with that of MgH 2 indicates that vanadium hydrides befit to improve the dehydrogenating properties of MgH 2 . Based on the analysis of the density of states (DOS) and the total valence electron density distribution of MgH 2 before and after V alloying, it was found that the improvement of the dehydrogenating properties of MgH 2 caused by V alloying originates from the increasing of the valence electrons at Fermi level (E F ) and the decreasing of the HOMO-LUMO gap ( H L E − Δ ) after V alloying. The catalysis effect of V on dehydrogenating kinetics of MgH 2 may attribute to a stronger bonding between V and H atoms than that between Mg and H atoms, which leads to nucleation of the α-Mg at the VH/MgH 2 interface in the MgH 2 -V systems easier than that in pure MgH 2 phase.

The hydrogen ab/desorption kinetic properties of doped magnesium hydride MgH2 systems by first principles calculations and kinetic Monte Carlo simulations

“…[7], the resulting heats of formation of the studied systems are listed in Table 1. It is shown, on the one hand, that DH ¼ À63.018kJ/mol.H 2 for MgH 2 structure is close to the theoretical values obtained using different methods: À63.18kJ/mol.H 2 [11], À75.99 kJ/mol.H 2 [12], À69.51 kJ/mol.H 2 [13], À82 kJ/mol.H 2 [21], À54.4 KJ/mol.H 2 [22], À71.98 KJ/mol.H 2 [23] and also close to the experimental value À76.15 ± 9.2kJ/ mol.H 2 obtained in Ref. [24].…”

Pressure-Driven Structural Phase Transitions and Superconductivity of Ternary Hydride MgVH6

“…In addition, based on the research of Im3̅ m CaH 6 and YH 6 with H clathrates, , Liang et al have reported that the ternary hydride Fd 3̅ m CaYH 12 has a pretty high T c (at 200 GPa, T c = 258 K) . However, the previous research on the Mg–V–H ternary systems mainly focused on the field of hydrogen storage, − and the structure evolution and properties of ternary Mg–V–H hydrides are less involved under high pressure. Based on the above viewpoint, we selected the ternary Mg–V–H hydride as an aim to investigate its structure evolution and superconductivity under high pressure.…”

A theoretical study of the influence of dopants on the dehydrogenation properties of VH2

“…Using the same code as in the supercell model, the total energy of V atoms is calculated to be -1979.06 eV. The total energy of H 2 is -2.320 Ry (-31.57 eV) [22] obtained by using the von Barth-Hedin exchange-correlation potential. The heat of formation of the VH 2 interfacial model is -65.61 kJ/mol (-0.68 eV) calculated from eq.…”