Density functional studies on structural, electronic and magnetic properties of Rh-n (n=9-20) clusters and O-H bond of methanol activation by pure and ruthenium-doped rhodium clusters

摘要

Methodical exploration is performed on Rh-n (n=9-20) clusters in the gas phase with all electron relativistic methods using density functional theory (DFT) within the generalized gradient approximation. Neutral clusters with even atoms of rhodium and ionic clusters containing odd atoms of rhodium are optimized with odd multiplicities, while neutral clusters containing odd rhodium atoms and ionic cluster having even atoms of rhodium are optimized with even multiplicities. DFT-based structural and reactivity parameters such as stability function, dissociation energy, HOMO-LUMO gap, ionization potential and electron affinity reveal higher stability of Rh-13, Rh-14 and Rh-19 clusters. Among these clusters, icosahedral Rh-13 is obtained to be the most stable. Magnetic moment and spin density analysis suggest nonzero magnetic moment for all clusters. DOS study reveals higher contribution of d electron density in bonding. Further, stable rhodium cluster-catalyzed O-H bond activation of methanol has been investigated. Rh - and Rh-14 are found to have higher activity towards O-H activation. Ruthenium-doped rhodium clusters have also been utilized to investigate the reactivity and catalytic activity of the same reaction and found to exhibit higher activity. Among all alloy clusters, Rh18Ru dissociates O-H more easily.