Evolution of the Spin Magnetic Moments and Atomic Valence of Vanadium in Vanadium doped Copper, Silver, and Gold Clusters.

The atomic structures, bonding characteristics, spin magnetic moments, and stability of VCu$_{\mathrm{x}}^{\mathrm{+}}$, VAg$_{\mathrm{x}}^{\mathrm{+}}$, and VAu$_{\mathrm{x}}^{\mathrm{+}}$ (x $=$ 3 - 14) clusters have been examined using density functional theory. Our studies indicate that the effective valence of vanadium is size-dependent and at small sizes some the valence electrons of vanadium are localized on vanadium while at larger sizes the 3$d$ orbitals of the vanadium participate in metallic bonding eventually quenching the spin magnetic moment. The electronic stability of the clusters may be understood through a split-shell model that partitions the valence electrons in either a delocalized shell or localized on the vanadium atom. A molecular orbital analysis reveals that in planar clusters the delocalization of the 3d orbital of vanadium is enhanced when surrounded by gold due to enhanced \textit{6s-5d} hybridization. Once the clusters become three-dimensional, this hybridization is reduced and copper most readily delocalizes the vanadium's valence electrons. By understanding these unique features, greater insight is offered into the role of a host materials electronic structure in determining the bonding characteristics and stability of localized spin magnetic moments in quantum confined systems.