Density Functional Theoretical Study on the Electronic Structure of RhO with Low Oxidation States.

RhO ( = 2-10) species are prepared by the reaction of the laser-ablated rhodium atoms with oxygen; furthermore, they are characterized by employing time-of-flight mass spectroscopy. To reveal the stable electronic structure, in this study, we performed the density functional theory calculations for the possible isomers of RhO . A total of 29 geometries were obtained including cyclic RhO, cyclic RhO, and ring-opening structures with doublet, quartet, sextet, and octet states. It is noteworthy that no Rh-Rh bond was observed for all the optimized RhO isomers including oxides, peroxides, superoxides, and oxygen groups. The optimized geometries were also confirmed to exhibit minimum structural energies by employing harmonic frequency analysis at the same energy level. Generally, two types of oxygen-bridged geometries were discovered with cyclic and pseudo-linear RhO , which contained one or more than one O groups. It is concluded that the cyclic structure comprises a lower energy than that observed in pseudo-linear structures. In addition, RhO tends to be unstable when the coordination groups change from O to O unit. Finally, the localized orbital bonding analysis indicates that Rh has oxidation states of 1 or 2 in cyclic RhO structures; this is true even in the presence of O, O , and O groups.