Structural properties of small copper clusters with a nickel impurity

The structural and magnetic stability of small NiCuN−1 clusters is determined by performing global structural optimizations within Kohn-Sham density-functional theory. The calculated structures for N ⩽ 5 atoms are compact and resemble, besides some interesting changes in bond length, the structures of the corresponding CuN clusters. The Ni ion occupies the most-coordinated atomic position, which reflects the dominant role of the sd hybridizations. For the optimal NiCuN−1 geometry the ground-state corresponds to a minimum-spin configuration (Sz = 0 or 1/2). Varying the total spin moment of the cluster reveals interesting correlations between cluster structure and magnetism. Low-energy spin excitations are found which involve similar energies as isomerizations. Structure and magnetic behavior are found to depend strongly on each other. The possible consequences of electron-correlation and finite-temperature effects are briefly discussed in the framework of the single-impurity Anderson model.