MgH_2-Nb体系解氢能力与电子结构的第一原理计算

采用第一原理赝势平面波方法,构建了一个NbH0.6/MgH2相界模型,研究了Nb合金化对MgH2解氢能力与电子结构的影响.结果显示:NbH0.6/MgH2相界的结构稳定性比MgH2相差,表明Nb合金化利于提高MgH2相的解氢能力;Nb对MgH2相解氢能力增强的主要原因在于Nb-H间电子相互作用比Mg-H间强,有利于促进NbH0.6相形核,并且α-Mg在MgH2-Nb体系的NbH0.6/MgH2相界中形核比在MgH2相中容易.

First-principles Calculation of Electronic Structure and Dehydrogenating Properties of MgH2-Nb Systems

A NbH_0.6/MgH₂ interface is designed and constituted in this work. A first-principles plane-wave pseudopotentials method based on Density Functional Theory (DFT) has been used to investigate the Niobium alloying effects on the dehydrogenating properties and electronic structure of magnesium hydride, i.e., MgH₂. A low absolute value of the negative heat of formation of NbH_0.6/MgH₂ interface compared with that of MgH₂ indicates Niobium hydrides befit to improve the dehydrogenating properties of MgH₂. Based on the analysis of the density of states (DOS) and the total electron density distribution of MgH₂ before and after Nb alloying, it was found that the catalysis effect of Nb on dehydrogenating kinetics of MgH₂ may attribute to a stronger bonding between Nb and H atoms than that between Mg and H atoms, which leads to nucleation of NbH_0.6 phase and the α-Mg at the NbH_0.6/MgH₂ interface in the MgH₂-Nb systems is easier than in pure MgH₂ phase.