甲基和羟基在Ir(111)表面吸附的密度泛函理论研究

在超原胞近似和slab模型基础上，采用周期性密度泛函理论，在0.11覆盖度（ML）下，对甲基与羟基在Ir(111)表面的吸附进行了研究，得到了甲基和羟基在Ir(111)表面不同吸附位置的吸附能和吸附构型，计算了它们的振动频率，同时分析了甲基和羟基共吸附于Ir(111)表面的情况。结果表明，甲基和羟基在Ir(111)表面的最稳定吸附位置都是top位，甲基是碳端向下吸附，羟基是通过氧端向下倾斜吸附。通过频率分析发现吸附后CH3中C-H键的对称伸缩振动、反对称伸缩振动以及剪切振动频率均发生了红移，而羟基中的O-H键的振动频率发生蓝移现象。通过计算对比发现甲醇分解为甲基和羟基过程是一个放热反应，从热力学角度来说该反应是可行的。

Density functional theory study of methyl/hydroxyl adsorption on Ir(111) surface

The adsorptions of methyl and hydroxyl on Ir(111) surface at 0.11 ML surface coverage are investigated using periodic density functional theory (DFT) based on the slab model and supercell approximation. The adsorption energies, structures and vibrational frequencies of the adsorption species on the Ir(111) have been calculated. The co-adsorptions of CH3 and OH on Ir(111) surfaces are also discussed. The results show that the CH3 is adsorbed preferentially at the top site, binding through the carbon atom. The most stable adsorption site of hydroxyl on the Ir(111) surface is the top site. Hydroxyl adsorbed on Ir(111) surface tiltes toward the surface through the oxygen atom. It is found that the C-H vibration frequencies for CH3 of symmetric stretching, asymmetric stretching, and scissoring vibration mode have redshifts and the O-H vibration frequency for OH has a blueshift after adsorption. The thermodynamical pathway are investigated of methanol decomposition to CH3 and OH. The decomposition process is slightly exothermic and thermodynamically favorable, which indicates that the process is expected.