Transition states, electronic structure, and magnetic properties of small-sized nickel clusters

Density functional computations of the electronic structure of small-sized nickel clusters $({\text{Ni}}_n,2\le n\le 12)$ have been carried out. We explored the potential energy surface at different spin multiplicities starting from guess structures obtained by statistical sampling. We focus this work on the search of the ground-state geometries and their magnetic properties. In some cases, close in energy geometries appear allowing a competition for the ground-state structure. For such cases, we investigated the energy profiles by searching for the transition states that connect structures belonging to different spin multiplicities.

Figure 1

Binding energy for the small-sized nickel clusters at the ground state.

Figure 2

Average magnetic moment per atom for the ground state at the PW91/SD level of theory and magnetic moment per atom from experiment, see Refs. (a) [58], (b) [64], and theory, (c) [7], (d) [52], (e) [65], (f) [54], (g) [57], (h) [56], and (i) [55].

Figure 3

Local magnetic moments in selected nickel clusters.

Figure 4

Spin densities for ${\text{Ni}}_n(2\le n\le 12)$ at the PW91/SD level of theory.

Figure 5

Free energy profiles connecting two spin multiplicities ground-state structures for selected nickel clusters. The square pyramid geometry is represented by $\blacksquare$ and the trigonal bipyramid is represented by $▴$.

Figure 6

Free energy profiles connecting two spin multiplicities ground-state structures for selected nickel clusters.

Figure 7

Free energy profiles connecting two spin multiplicities ground-state structures for selected nickel clusters.