Determining the magnetic order of Con+ (n ≤ 5) clusters by using multi-configurational calculations

Abstract

The magnetism of transition metal clusters have been for decades a complicated puzzle, with experimental results disagreeing with calculations performed within the density functional theory formalism. In this talk, I will provide a key to this puzzle by investigating the lowest-energy spin states of cobalt cluster, Con+ (n ≤ 5), using advanced CASSCF/NEVPT2 calculations with very large active spaces. These very computationally demanding calculations are able to correctly predict the measured spin states of the clusters, in contrast to the widely used density functional theory, with results that depend on the selected exchange-correlation functional. The reasons for the failure of density functional theory, in opposition to CASSCF/NEVPT2, will be discussed, providing a solid framework for investigating other transition metal and transition metal oxide clusters.