氢在钯单晶表面的解离与在体相的扩散

氢分子在金属表面的解离吸附与氢原子在金属体相的扩散是个典型的表面过程.前者在甲烷化及合成氨等基础化工反应中起着关键作用;后者常常导致金属材料的脆化与断裂,但过渡金属及其合金是安全和优良的储氢材料.因此,研究氢分子在金属表面的解离吸附与氢原子在金属体相的扩散,是多相催化与金属物理广泛感兴趣的课题,具有重要的理论和应用价值.本文采用分子动力学方法初步探讨了二者之间的关联.分子催化动力学为从微观层次上研究上述课题提供了一种理论方法.本文采用经过我们改进的半经验LEPS方法,计算了氢分子在Pd(100)和(110)晶面的解离和氢原子在钯表面与体相扩散的相互作用位能面,并根据计算结果探讨了其微观机理.

THE SURFACE DISSOCIATION AND BULK DIFFUSION OF HYDROGEN ON PALLADIUM SINGLE CRYSTAL SURFACES

By means of the improved semi-empirical LEPS method, the potential energy surfaces of the interaction between hydrogen and palladium single crystal surface, Pd(100) and Pd(110) , have been calculated. The calculated results show that the H2 molecule is inserted into a four-fold hollow site of Pd(110) and a stable adsorption state is formed under the Pd surface, since the internuclear distance of H2 is little larger than the equilibrium one. It is clear that H atom diffusion into the metal bulk decreases the energy of the system, while H2 molecule diffusion into the metal bulk increases the energy. This implies that the atomic diffusion is easier to occur.