H_2O分子在Fe(100),Fe(110),Fe(111)表面吸附的第一性原理研究

First principles study of H_2O molecule adsorption on Fe(100),Fe(110)and Fe(111) surfaces

采用第一性原理研究了H2O分子在Fe(100),Fe(110),Fe(111)三个高对称晶面上的表面吸附.结果表明,H2O分子在三个晶面上的最稳定结构皆为平行于基底表面的顶位吸附结构.H2O分子与三个晶面相互作用的吸附能及几何结构计算结果表明H2O分子与三个晶面的相互作用程度不同,H2O分子与Fe(111)晶面的相互作用最强,其次是Fe(100),相互作用最弱的是Fe(110)表面,而这与晶面原子的排列密度相关.吸附体系的电子结构计算结果也得出了相似的结论.同时电荷布居分析表明,H2O分子与Fe表面相互作用时,O原子与基底原子之间的电荷交换使基底Fe原子表面带负电,导致表面电位降低,也促使Fe表面更易于发生电化学腐蚀反应.

The adsorption of H2O on Fe（ 100）, Fe（110） and Fe（ 111 ） crystal surfaces were studied by first principles. The calculation results indicate that H2O monomers bind preferentially at top sites and lie nearly flat on the three crystal surfaces. The results of adsorption energy and geometry structure show that the effect of H2O adsorbed on three iron crystal surfaces is different. The strongest interaction occurred between H2O and Fe（111） crystal surface and the weakest interaction is between H2O and Fe（110） crystal surface. Such relationship is related to the different surface atoms density. The similar conclusion can be drawn from the calculation results of electronic structure and Mulliken analysis. The Mulliken analysis also indicates that when H20 is adsorbed on the iron surface, charge exchange between O atom and Fe atom make the iron surface negatively charged and reduce the surface potential, which promote the electrochemical corrosion of iron surfaces.