H_2O在Fe_3O_4(111)表面吸附的结构及热力学研究(英文)

Structures and energetics of H_2O adsorption on the Fe_3O_4(111) surface

使用密度泛函理论(GGA/PBE)对H2O在Fetet1-和Feoct2-终结Fe3O4(111)表面的吸附行为进行了研究。对于Fetet1-终结表面,在1/5 ML覆盖度下,带有氢键的H2O分子以及异裂解离的结构具有最高的稳定性,而类似水合氢离子的OH3+-OH结构出现在2/5 ML覆盖度下,其次为带有氢键的水的聚合体。这些结果与实验中观测到的现象一致。对于Feoct2-终结表面,在1/6 ML覆盖度下,分子态H2O的吸附是有利的,而在1/3 ML覆盖度下多种吸附形式共存。H2O吸附在Fetet1-终结表面比吸附在Feoct2-终结表面热力学上更有利。此外,通过计算局域态密度(LDOS)对吸附机理进行了分析。

Water adsorption on the Fetee1-terminated and Feoct2-terminated surfaces of Fe3O4 （111） has been calculated at the level of density functional theory （GGA/PBE）. On the Fetet1 -terminated surface at 1/5 monolayer （ ML）, the molecular adsorption mode with a hydrogen bond and the heterolytically dissociative mode show the highest stability, whereas the hydronium-ion-like structure OH^3 ＋ OH becomes possible at 2/5 ML, followed by the hydrogen-bonded water aggregate. These results agree well with the available experimental observations. For Feoct2-terminated surface, the molecular water prefers to adsorb on the surface Feoct2 atom at 1/6 ML, whereas other adsorption modes become possible and may coexist at 1/3 ML. The Ftet1,-terminated surface is more favorable than the Foct2-terminated surface for water adsorption. The adsorption mechanism has been analyzed on the basis of the calculated local density of state.