On the Ground State Structures of Bimetallic Ni<em>_m</em>Cu<em>_n</em> (<em>m</em> + <em>n</em> &#x02264; 6) Clusters and Their Reactivity toward O₂

Abstract

Extensive auxiliary density functional theory (ADFT) computations were performed to study the most stable structures, stabilities and chemical reactivity toward O2 of bimetallic NimCun (m + n ≤ 6) clusters. The shape of the most stable structures changes as the number of Ni and Cu atoms of the system under study increases with a consequent change of the energy, magnetic and reactivity properties. All obtained minimum-energy structures for these bimetallic systems composed with three and four atoms possess triangular and rhombic structures, respectively. According to our computations, the most stable structures for Ni4Cu, Ni3Cu2, and Ni2Cu3 clusters are trigonal-bipyramidal, while, for the NiCu4 cluster, two structures were identified as the most stable (with planar and trigonal-bipyramidal structures, respectively). The most stable structure for the Ni5Cu cluster is octahedral, while for the Ni4Cu2, Ni3Cu3, Ni2Cu4, and NiCu5 clusters, an incomplete pentagonal bipyramid was found as the ground-state structure. For all cluster sizes, as the number of Cu atoms in the system increases, the magnetic moment per atom tended to decrease. The O2 adsorption on bimetallic NimCun (m + n = 6) clusters is more favored when O2 binds by a bridge-type bond. Moreover, our computations indicate that O2 is preferentially adsorbed on the Ni atoms of bimetallic NimCun (m + n = 6) clusters.