空位缺陷对氧分子在方铅矿(100)表面吸附的影响

Effect of vacancy defects on oxygen molecule adsorption on galena surface (100)

应用基于密度泛函理论(DFT)的第一性原理,采用广义梯度近似(GGA)和平面波超软赝势方法,研究空位缺陷对氧分子在方铅矿(100)表面吸附行为的影响,并比较和分析它们及理想表面的Mulliken电荷布居、电子密度差图和态密度等。结果表明:铅空位比硫空位难形成,两种空位缺陷表面对氧分子有强烈的化学吸附作用,其吸附能均高于理想表面的,说明空位缺陷可以促进氧分子在方铅矿表面的吸附。氧分子在理想表面及铅空位表面发生了解离吸附,氧原子与硫原子形成了共价键;氧分子在硫空位表面没有发生解离吸附,氧原子与表面的铅原子表现出较强的离子相互作用力。

The effects of vacancy defects on oxygen molecule adsorption on galena surface （100） were studied by applying the general gradient approximation （GGA） and plane-wave ultrasoft pseudopotential method based on the first principle of density functional theory （DFT）. The Mulliken charges population, electron density difference maps and density of states of oxygen atom and surface atoms before and after 02 adsorption were analyzed. The results show that the formation of Pb-vacancy on the galena surface （100） is more difficult than S-vacancy, and the chemical adsorption of oxygen molecule on both Pb-vacancy and S-vacancy surfaces occurs, and their adsorption energies are more negative than those on the perfect surface, which indicates that vacancy defect can encourage the oxygen molecule adsorption on galena surface. The dissociated adsorption of oxygen molecule occurs on the perfect and Pb-vacancy surfaces, and a covalent bond is formed between oxygen atom and sulfur atom. The oxygen molecule adsorbing on S-vacancy surface is not dissociated. Ionic interaction between oxygen atom and lead atom is very strong.