We systematically study the equilibrium geometries and electronic and magnetic properties of Ge and VGe (n = 1-19) clusters using the density functional theory approach within the generalized gradient approximation. Endohedral structures in which the vanadium atom is encapsulated inside a Ge cage are predicted to be favored for n ≥ 10. The dopant V atom in the Ge clusters has not an immediate effect on the stability of small germanium clusters (n < 6), but it largely contributes to strengthen the stability for n ≥ 7. Our study enhances the large stability of the VGe cluster, which presents an O symmetry cagelike geometry and a peculiar electronic structure in which the valence electrons of V and Ge atoms are delocalized and exhibit a shell structure associated with the quasi-spherical geometry. Consequently, this cluster is proposed to be a good candidate to be used as the building blocks for developing new materials. The cluster size dependence of the stability, the vertical ionization potentials, and electron affinities of Ge and VGe are presented. Magnetic properties and the partial density of states of the most stable VGe clusters are also discussed.

Structures, energetics, and electronic properties of noble metal-doped germanium (MGe with M = Cu, Ag, Au; n = 1-19) clusters are systematically investigated by using the density functional theory (DFT) approach. The endohedral structures in which the metal atom is encapsulated inside of a germanium cage appear at n = 10 when the dopant is Cu and n = 12 for M = Ag and Au. While Cu doping enhances the stability of the corresponding germanium frame, the binding energies of AgGe and AuGe are always lower than those of pure germanium clusters. Our results highlight the great stability of the CuGe cluster in a D structure and, to a lesser extent, that of AgGe and AuGe, which exhibits a hollow cage-like geometry. The sphere-type geometries obtained for n = 10-15 present a peculiar electronic structure in which the valence electrons of the noble metal and Ge atoms are delocalized and exhibit a shell structure associated with the quasi-spherical geometry. It is found that the coinage metal is able to give both s- and d-type electrons to be reorganized together with the valence electrons of Ge atoms through a pooling of electrons. The cluster size dependence of the stability, the frontier orbital energy gap, the vertical ionization potentials, and electron affinities are given.

The structural, electronic and magnetic properties of niobium and tantalum doped germanium clusters MGen (M = Nb, Ta and n = 1-19) are investigated by first principles calculations within the Density Functional Theory approach (DFT). The growth pattern behaviors, stabilities, and electronic properties are presented and discussed. Endohedral cagelike structures in which the metal atom is encapsulated are favored for n ≥ 10. The doping metal atom contributes largely to strengthen the stability of the germanium cage-like structures with the binding energy ordered as follows BE(Gen+1) < BE (VGen) < BE(NbGen) < BE(TaGen). Our results highlight the relative high stability of NbGe15, TaGe15 and VGe14.