Pd金属表面CO吸附态的密度泛函计算及应用  

Density functional calculations and appications of CO adsorption on Pd metallic surfaces

作　　者：李平[1] 

机构地区：[1]四川大学化学学院化学系,四川成都610064

出　　处：《化学研究与应用》2005年第6期741-748,共8页Chemical Research and Application

摘　　要：通过对CO在Pd表面上形成的各种化学吸附态的理论计算,借助B3LYP/3-21G*方法,确定了各种吸附态Pdn-CO(n=1-5,7,9)的优化几何构型、相对稳定性、反应活性和吸附性质。其中μ3-Pd3CO和μ4-Pd4CO比线式和桥式更易使CO活化,而且相对难解吸,表现出较好的催化性能。论文还就实验FT-IR谱峰,模拟了一些未见实验报道的吸附态,同时讨论了其稳定性和理论伸展振动频率。最后运用多组态相互作用(CASS-CF/3-21G*)计算了主要吸附态的离解能,得到Pdn-CO较Pdn-OC稳定的结论。根据各吸附态的稳定性和对CO的活化程度,确定了桥式态IR吸收是实验跟踪反应的最佳吸收带。The theoretical structures of various possible CO adsorptive states on Pd metallic surfaces have been analyzed through ap- prehending the experimental IR frequnencies. The relative stability of Pdn - CO（ n = 1 - 5,7,9 ） intermediates and the geometrical optimization have been calculated at the B3LYP/3 -21G＊ level to reveal their adsorptive properties and reactivity. We have also simulated several fine structures of adsorptive states and calculated their IR frequencies of the - C = O stretching vibration, and the results have explained the experimental IR data. The possible intermediates of μ3-Pd3 CO and μ4-Pd4 CO are easy to active CO bonds and hard to dissociate from Pd surface relatively,therefore,they have the better catalysis capability, the bond orders between CO molecules and Pd atoms on various surfaces have been obtained to discuss the chemical bonding on surfaces. The dissociation energy at the CASSCF/3 -21G＊ level have concluded that the Pdo -CO are more stable than the Pdn -OC. The bridge states can be applied to track CO adsorption cataysis reactions due to its stability and the extent of activation CO. Moreover,the intensit/es of its IR bands are sensitive to the adsorptive conditions.

关 键 词：Pdn-CO吸附态 活性 IR频率 离解能 稳定化能 B3LYP 

分 类 号：O641.121[理学—物理化学]