【摘要】 本文用密度泛函理论(DFT)的总能计算研究了一氧化碳和氢原子在Ni(111)表面上p(2×2)共吸附系统的原子结构和电子态,结果表明CO和H原子分别被吸附于两个对角p(1×1)元胞的hcp和fcc位置.以氢分子和CO分子作为能量参考点,总吸附能为2.81eV,相应的共吸附表面功函数φ为6.28eV.计算得到的C—O,C—Ni和H—Ni的键长分别是1.19,1.96和1.71,并且CO分子以C原子处于hcp的谷位与金属衬底原子结合.衬底Ni(111)的最外两层的晶面间距在吸附后的相对变化分别是+1.6%(Δd12)和+0.4%(Δd23).对于Ni(111)表面CO和氢原子p(2×2)单吸附结构,计算结果表明在Ni(111)p(2×2)/H表面吸附系统中,fcc位置吸附的氢原子其能量最低,吸附高度是0.90;而在Ni(111)p(2×2)/CO表面中,hcp位置吸附的CO其能量最低,吸附高度是1.33.在Ni(111)p(2×2)/(CO+H)中每个CO和H原子之间的相互作用能约为0.60eV.由于Ni(111)的存在使得CO和H原子作用增强,为更好地理解Ni(111)作为催化表面在Fisher-Tropsch反应中的作用提供了一定的基础.更多还原

【Abstract】 In this article a first-principles total energy calculation of the atomic geometry and electronic structure of carbon-monoxide and hydrogen co-adsorbed on Ni(111) p(2×2) surface at a coverage of 0.25 ML is reported. The optimized atomic geometry is in good agreement with the most recently reported LEED experiment on Ni(111) p(2×2)/(CO+H) co-adsorbed system. The carbon-monoxide is predicted to be adsorbed on the hcp site while hydrogen atom occupies the fcc site, and both adsorbates locate on opposite p(1×1) cells within a p(2×2) supercell. The adsorption energy of CO and H in this configuration is 2.81 eV with respect to the CO and H-2 molecule and the surface work function is calculated to be 6.28 eV in comparison with 5.23 eV of clean Ni(111) surface. The bond lengths of C—O, C—Ni, and H—Ni are estimated to be 1.19?, 1.96?, and 1.71?, respectively, and the substrate interlayer distance variations, Δd- 12 and Δd- 23 , are calculated to be +1.6% and +0.4%, respectively. The chemisorptions of CO and H atom on the Ni(111) p(2×2) surface were calculated in the same way and the adsorption heights of CO and H were evaluated to be 1.33? and 0.90?, respectively. The interaction energy between CO and H in the best fit geometry of Ni(111) p(2×2)/(CO+H) system is about 0.60 eV, which could be taken as the essential factor for the realization of Fisher-Tropsch reaction.更多还原