Density Functional And Dynamics Study Of The Dissociative Adsorption Of Hydrogen On Mg (0001) Surface

摘要

A first principles study is performed to investigate the adsorption characteristics of hydrogen on magnesium surface. Substitutional and on-surface adsorption energies are calculated for Mg (0001) surface alloyed with the selected elements. To further analyze the hydrogen-magnesium interaction, first principles molecular dynamics method is used which simulates the behavior of H_2 at the surface. Also, charge density differences of substitutionally doped surface configurations were illustrated. Accordingly, Mo and Ni are among the elements yielding lower adsorption energies, which are found to be -9.2626 and -5.2995 eV for substitutionally alloyed surfaces, respectively. In light of the dynamic calculations, Co as an alloying element is found to have a splitting effect on H_2 in 50 fs, where the first hydrogen atom is taken inside the Mg substrate right after the decomposition and the other after 1300 fs. An interesting remark is that, elements which acquire higher chances of adsorption are also seen to be competent at dissociating the hydrogen molecule. Furthermore, charge density distributions support the results of molecular dynamics simulations, by verifying the distinguished effects of most of the 3d and 4d transition metals.