Quantum chemical study of atomic structure evolution of Co/C (x 2.8) composites

Avramov, P.; Naramoto, Hiroshi*; Sakai, Seiji; Narumi, Kazumasa; Lavrentiev, V.*; Maeda, Yoshihito

The main features of the local atomic structure of novel Co/C (x 2.8) complex mixtures were studied using the B3LYP/6-31G method for a set of low and high energy Co(C) (n = 1, 2, m = 2, 3) clusters in low and intermediate spin states. For the n = 1 isomers the spin state S = 1/2 is energetically preferable whereas the low energy isomers of n = 2 have an intermediate spin state of S = 1. The (6-6 edge of C) type of cobalt ion coordination is preferable for both n = 1 and n = 2 cases. The (coordination with 6-5 edge) and even the (C fragment) types can serve as low and high energy intermediates for the cobalt ion's migration around the C cage. Formation of cobalt dimers can be the final stage of evolution of Co/C atomic structure approaching the equilibrium atomic geometry.