Banerjee S, Pillai C G S, Majumder C
Chemistry Division, BARC, Trombay, Mumbai 85, India.
J Chem Phys. 2008 Nov 7;129(17):174703. doi: 10.1063/1.3000673.
Using first-principles calculations we have investigated the interaction of hydrogen molecules with clean and M (Ti, V, and Ni) doped Mg(0001) surfaces. The calculations have been carried out using plane-wave-based pseudopotential method under the formalism of density functional theory. First we have calculated the stability of the M atoms on the Mg surface. On the basis of the energetic criteria, we found that all these M atoms prefer to substitute one of the Mg atoms from the second layer than the top surface atom. In the second step we have studied the interaction of a hydrogen molecule with the clean and doped Mg surface. The results show that for M atoms at the surface, the hydrogen molecule undergoes spontaneous dissociative chemisorptions. However, for M atoms in the second layer, it requires to cross an activation barrier to undergo molecular dissociation. Furthermore, to understand the mobility of hydrogen atoms on the surface we have calculated the diffusion energy barriers for the M doped surface. Contrary to the molecular dissociation behavior, it is found that the mobility of hydrogen atoms on the surface is easier if the M atoms are placed in the second layer in comparison to that in the top surface layer. It is believed that the results of the present study provide useful information based on the first-principles calculations for synthesizing Mg based materials for hydrogen storage with optimal performance.
我们使用第一性原理计算方法研究了氢分子与清洁的以及M（Ti、V和Ni）掺杂的Mg(0001)表面之间的相互作用。这些计算是在密度泛函理论框架下使用基于平面波的赝势方法进行的。首先，我们计算了M原子在Mg表面的稳定性。基于能量标准，我们发现所有这些M原子更倾向于替代第二层中的一个Mg原子，而不是顶层表面原子。第二步，我们研究了氢分子与清洁的和掺杂的Mg表面的相互作用。结果表明，对于表面的M原子，氢分子会发生自发的解离化学吸附。然而，对于第二层中的M原子，它需要跨越一个活化能垒才能发生分子解离。此外，为了理解氢原子在表面上的迁移率，我们计算了M掺杂表面的扩散能垒。与分子解离行为相反，发现如果M原子位于第二层，氢原子在表面上的迁移率比位于顶层表面层时更容易。据信，本研究的结果基于第一性原理计算为合成具有最佳性能的储氢镁基材料提供了有用信息。
