Density functional study on the structural, frontier orbital, electronic, and magnetic properties of the transitional metal clusters Pd-5(CO)(n) (n=1 to 6)

The generalized gradient approximation based on density functional theory is used to analyze the structural, electronic, and magnetic properties of the transition metal clusters Pd-5(CO)(n) (n=1 to 6). For Pd5CO, the most stable isomer is the singlet state structure with C atom adsorbed on the hollow site in the form of CO molecule, as same as the conclusion reported by Zanti et al (Eur. J. Inorg. Chem. 2009, 3904). In the most stable isomers of Pd-5(CO)(2) and Pd-5(CO)(3), the first CO molecule is adsorbed on the hollow site, while the second and the third CO molecules are adsorbed on the bridge sites, whereas, for the most stable Pd-5(CO)(n) (n=4,5,6), all CO molecules are adsorbed on the bridge sites. It is known from the adsorption energy that Pd-5(CO)(2) should be the most possible adsorption product. The energy gap indicates that Pd-5(CO)(n) (n=1 to 6) have the enhanced dynamical stability compared to Pd-5, and Pd-5(CO)(3) should be most dynamically stable of all. The chemisorptions of CO molecules onto the Pd-5 cluster are non-dissociative and the strength of C-O bond becomes weaker while more CO molecules are adsorbed. Along with the increase of the CO molecules in Pd-5(CO)(n) (n=1 to 6), the ability for detaching electrons is weakened and that for obtaining electrons is improved. The magnetic moment of Pd-5 is 2 mu B, however, Pd-5(CO)(n) (n=1 to 6) have no magnetic moment.