Pd_6簇与H_2分子相互作用的密度泛函理论研究

Density Functional Theory Study on the Interaction of Pd_6 with Multiple H_2

通过相对论有效核势密度泛函理论计算 ,优化了Pd6(H) 2 和Pd6(H) 4 等簇的平衡几何结构 ,预测了氢分子在Pd6簇表面上的吸附行为与活化解离性质 .计算结果表明 ,单态的Pd6簇可以活化两个氢分子 ;第一个H2 和第二个H2 吸附解离过程速率决定步骤的能垒分别是 66 4和 2 4 5kJ/mol.在形成的分子氢配合物Pd6(H2 )和Pd6(H) 2 H2 中 ,H2 主要作为给电子配体 .在最稳定的二氢簇合物Pd6(H) 2 中 ,H倾向与 3个Pd相互作用 ,形成面位氢的多核成键吸附方式 .

Equilibrium geometries of Pd6H2, Pd-6(H)(2) and Pd-6(H)(4) clusters and multiple H-2 adsorption and dissociation on Pd-6 were investigated by density functional theory calculations with the relativistic effective core potential. Present calculations show that barriers of the rate-determining steps for the first H-2 and the second H-2 activation processes are 66.4 and 24.5 kJ/mol, respectively. In the dihydrogen complexes the H-2-ligand behaves as donor in the molecular bonding between H-2 and Pd-6. Chemisorbed hydrogen atoms prefer to bind the Pd-3 facet of Pd6 in the most stable hydride complex Pd-6(H)(2).