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arXiv 0811.2342cond-mat.mtrl-sci
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氢在过渡金属(=Ti,Zr,V,Fe,Ru,Co,Rh,Ni,Pd,Cu,Ag)掺杂Mg(0001)表面的解离和扩散

Hydrogen Dissociation and Diffusion on Transition Metal(=Ti,Zr,V,Fe,Ru,Co,Rh,Ni,Pd,Cu,Ag)-doped Mg(0001) Surfaces

Monica Pozzo, Dario Alfe`

摘要:

镁块体吸氢动力学受两个主要活化过程的影响:H $_2$分子的解离和原子H向块体中的扩散。为了具有快速吸收动力学,两种活化处理都需要具有低屏障。本文采用从头算密度泛函理论研究了H $_2$在TM(=Ti,V,Zr,Fe,Ru,Co,Rh,Ni,Pd,Cu,Ag)掺杂的Mg(0001)表面的解离和H原子的扩散.计算表明,在元素周期表左侧用TM掺杂表面消除了分子解离的障碍,但H原子与TM的结合非常强,因此阻碍了扩散。相反,元素周期表右侧的TM不结合H,然而,它们不显著降低解离H $_2$的屏障。我们的研究结果表明,铁,镍和铑,在一定程度上的钴和钯,都是例外,结合低活化势垒的两个过程中,镍是最好的选择。

英文摘要:

The kinetics of hydrogen absorption by magnesium bulk is affected by two main activated processes: the dissociation of the H$_2$ molecule and the diffusion of atomic H into the bulk. In order to have fast absorption kinetics both activated processed need to have a low barrier. Here we report a systematic ab-initio density functional theory investigation of H$_2$ dissociation and subsequent atomic H diffusion on TM(=Ti,V,Zr,Fe,Ru,Co,Rh,Ni,Pd,Cu,Ag)-doped Mg(0001) surfaces. The calculations show that doping the surface with TM's on the left of the periodic table eliminates the barrier for the dissociation of the molecule, but the H atoms bind very strongly to the TM, therefore hindering diffusion. Conversely, TM's on the right of the periodic table don't bind H, however, they do not reduce the barrier to dissociate H$_2$ significantly. Our results show that Fe, Ni and Rh, and to some extent Co and Pd, are all exceptions, combining low activation barriers for both processes, with Ni being the best possible choice.

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