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首页> 外文期刊>Physical review >Surface energetics of alkaline-earth metal oxides: Trends in stability and adsorption of small molecules
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Surface energetics of alkaline-earth metal oxides: Trends in stability and adsorption of small molecules

机译：碱土金属氧化物的表面能学：小分子的稳定性和吸附趋势

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摘要

We present a systematic theoretical investigation of the surface properties, stability, and reactivity of rocksalt type alkaline-earth metal oxides including MgO, CaO, SrO, and BaO. The accuracy of commonly used exchange-correlation density functional (LDA, PBE, RPBE, PBEsol, BEEF-vdW, and hybrid HSE) and random-phase approximation (RPA) is evaluated and compared to existing experimental values. Calculated surface energies of the four most stable surface facets under vacuum conditions, the (100) surface, the metal and oxygen terminated octopolar (111), and the (110) surfaces, exhibit a monotonic increase in stability from MgO to BaO. On the MgO(100) surface, adsorption of CO, NO, and CH4 is characterized by physisorption while H_2O chemisorbs, which is in agreement with experimental findings. We further use the on-top metal adsorption of CO and NO molecules to map out the surface energetics of each alkaline-earth metal oxide surface. The considered functionals all qualitatively predict similar adsorption energy trends. The ordering between the adsorption energies on different surface facets can be attributed to differences in the local geometrical surface structure and the electronic structure of the metal constituent of the alkaline-earth metal oxide. The striking observation that CO adsorption strength is weaker than NO adsorption on the (100) terraces as the period of the alkaline-earth metal in the oxide increases is analyzed in detail in terms of charge redistribution within the σ and π channels of adsorbates. Finally, we also present oxygen adsorption and oxygen vacancy formation energies in these oxide systems.
机译：我们对包括MgO，CaO，SrO和BaO在内的岩盐型碱土金属氧化物的表面性质，稳定性和反应性进行了系统的理论研究。评估了常用交换相关密度函数（LDA，PBE，RPBE，PBEsol，BEEF-vdW和混合HSE）和随机相位近似（RPA）的准确性，并将其与现有实验值进行了比较。在真空条件下，四个最稳定的表面，（100）表面，金属和氧封端的八极（111）和（110）表面的计算表面能显示出从MgO到BaO的稳定性单调增加。在MgO（100）的表面上，CO，NO和CH4的吸附以物理吸附为特征，而H_2O的化学吸附则与实验结果一致。我们进一步利用CO和NO分子在顶部的金属吸附来绘制每个碱土金属氧化物表面的表面能。所考虑的功能都定性地预测了相似的吸附能趋势。不同表面小面上的吸附能之间的排序可以归因于碱土金属氧化物的局部几何表面结构和电子结构的差异。随着吸附物中σ和π通道内电荷的重新分布，随着氧化物中碱土金属周期的增加，CO吸附强度比（100）阶地上的NO吸附弱，这一惊人发现得到了详细分析。最后，我们还介绍了这些氧化物体系中的氧吸附和氧空位形成能。

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  • 来源
    《Physical review》 |2015年第15期|155401.1-155401.10|共10页
  • 作者

    Michal Bajdich; Jens K. Norskov; Aleksandra Vojvodic;

  • 作者单位

    SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory and Department of Chemical Engineering, Stanford University, 443 via Ortega, Stanford, California 94305, USA;

    SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory and Department of Chemical Engineering, Stanford University, 443 via Ortega, Stanford, California 94305, USA;

    SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory and Department of Chemical Engineering, Stanford University, 443 via Ortega, Stanford, California 94305, USA;

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  • 关键词

    impurity and defect levels; energy states of adsorbed species; total energy and cohesive energy calculations;

    机译：杂质和缺陷水平;吸附物质的能量状态;总能量和内聚能计算;

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