Giordano Livia, Carrasco Javier, Di Valentin Cristiana, Illas Francesc, Pacchioni Gianfranco
Dipartimeto di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 53-20125 Milano, Italy.
J Chem Phys. 2006 May 7;124(17):174709. doi: 10.1063/1.2189852.
The bonding, spin density related properties, and vibrational frequency of CO bound to single Au atom in the gas-phase or supported on MgO surfaces have been investigated with a variety of computational methods and models: periodic plane waves calculations have been compared with molecular approaches based on atomic orbital basis sets; pseudopotential methods with all electron fully relativistic calculations; various density functional theory (DFT) exchange-correlation functionals with the unrestricted coupled-cluster singles and doubles with perturbative connected triples [CCSD(T)]. AuCO is a bent molecule but the potential for bending is very soft, and small changes in the bond angle result in large changes in the CO gas-phase vibrational frequency. At the equilibrium geometry the DFT calculated vibrational shift of CO with respect to the free molecule is about -150 cm(-1), whereas smaller values -60-70 cm(-1) are predicted by the more accurate CCSD(T) method. These relatively large differences are due to the weak and nonclassic bonding in this complex. Upon adsorption on MgO, the CO vibrational shift becomes much larger, about -290 cm(-1), due to charge transfer from the basic surface oxide anion to AuCO. This large redshift is predicted by all methods, and is fully consistent with that measured for MgOAuCO complexes. The strong influence of the support on the AuCO bonding is equally well described by all different approaches.
已使用多种计算方法和模型研究了气相中与单个金原子结合或负载在氧化镁表面上的一氧化碳的键合、自旋密度相关性质和振动频率：将周期性平面波计算与基于原子轨道基组的分子方法进行了比较；赝势方法与全电子完全相对论计算进行了比较；各种密度泛函理论（DFT）交换相关泛函与无限制耦合簇单双激发并带有微扰连接三激发[CCSD(T)]进行了比较。AuCO是一个弯曲分子，但弯曲势能非常软，键角的微小变化会导致CO气相振动频率的大幅变化。在平衡几何构型下，DFT计算得出的CO相对于自由分子的振动位移约为-150 cm⁻¹，而更精确的CCSD(T)方法预测的值较小，为-60至-70 cm⁻¹。这些相对较大的差异是由于该配合物中弱的非经典键合所致。吸附在MgO上时，由于从碱性表面氧化物阴离子向AuCO的电荷转移，CO的振动位移变得更大，约为-290 cm⁻¹。所有方法都预测到了这种大的红移，并且与MgOAuCO配合物的测量结果完全一致。载体对AuCO键合的强烈影响在所有不同方法中都得到了很好的描述。
