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zhangzhiweia(金币+5, 翻译EPI+1):谢谢，您辛苦了 2010-12-11 18:21:55
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The most energetically stable configuration was obtained from the H adsorption by using elastic band method and was utilized to characterize probable electrode reaction pathways of adsorption H on Pt(100) surface by maping out the minimum-energy paths(MEP). A (4×1) surface unit cell with a slab of three layers thickness(36 Pt atoms) was selected to model adsorption of H on Pt(100) surface(the single structure determined lattice constant of 8.324Å was used for the production of Pt(100) surface). The slab was repeated periodically with a 13.962Å in vacuum region between the slabs. Plausible intermediates for the H-Pt(100) interactions was initially optimized by placing H atoms at two different active sites on the Pt(100) surface, including “Pt-bridge site and Pt-hollow site”, corresponding to the structure of Pt(100) surface. During electrode reaction，the anode would lose electrons. After optimization，the adsorption energy and Pt-H distance for hydrogen on Pt(100) surface are presented in Table 1. The negative adsorption energy comes from the computer procedure that the geometry optimization is carried out only in no-spin-polarization calculation. As shown in Table 1, the adsorption energy for bridge site is larger than that for the hollow site. Namely, bridge site on the terrace is more stable after geometry optimization, the hollow site on the terrace might be under the intermediate state. Furthermore, Pt-H distance for hydrogen on Pt(100) surface(seen from table 1) was analyzed. Before electrode reaction, the Pt-H distances for the hollow site and bridge site are 2.035 Å, 1.613 Å respectively. The H-Pt distance at bridge site is shorter than that at hollow site. That is, the bridge site is more stable than another. After electrode reaction, the Pt-H distances for the hollow site and bridge site are 2.029 Å and1.607 Å, respectively. Zhang******* reported the morse Potential of 1.79 Å for calculating Pt-H distance at the most stable state, similar to our result. The distance of Pt-H was found to become shorter in the electrode reaction. The Pt-H distance for the bridge sites is shorter as compared with that for the hollow sites, indicating that the adsorption energy for the latter will be larger. In conclusion, the best adsorption of H on Pt(100) occurs in the bridge site. |
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