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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.
On the basis of supramolecular approximation and slab model, the adsorption of methyl group and hydroxyl group on Ir (111) surface was investigated by periodic density functional theory at 0.11 coverage (ML), and the methyl and Hydroxyl groups on the Ir (111) surface at different adsorption sites, the vibrational frequencies were calculated and the case of co-adsorption of methyl groups and hydroxyl groups on the Ir (111) surface was also discussed.The results showed that the methyl groups and the hydroxyl groups The most stable adsorption sites on the Ir (111) surface were the top sites, the methyl groups were adsorbed on the carbon side and the hydroxyl groups were desorbed downward through the oxygen side.The symmetric stretching vibration of CH bond in CH3 was found by frequency analysis, The anti-symmetric stretching vibration and the shear vibration frequency all undergo a red shift, while the vibrational frequency of the OH bond in the hydroxyl group shifts bluely.According to the calculation and comparison, it is found that the decomposition of methanol into methyl and hydroxyl is an exothermic reaction. From the thermodynamic point of view, The reaction is feasible.