Study of pure and doped hydrogenated germanium cages: a density functional investigation.

In this paper we present an ab initio electronic-structure calculation performed using density functional theory (DFT) with a polarized basis set (SDD) within the spin polarized generalized gradient approximation for pure and divalent transition metal doped hydrogenated germanium nanocluster cages Ge(n)H(n)M (M = Zn, Cd and Hg, n = 6-28). In the first step of the calculation, geometrical optimizations of the nanoclusters are done. In the next step only the ground state optimized geometries are used to calculate the binding energy (E(b)), HOMO-LUMO gap (Delta E(g)) and embedding energy of the clusters. To study the optical behaviour of the clusters, IR and Raman spectra are calculated. Further calculations on cation and anion clusters have been done only for pure and Zn doped clusters to obtain their vertical ionization potential (VIP), adiabatic electron affinity (AEA) and chemical potential.