Conclusions
In this present report, we analyzed the stability and electronic
properties of M@Ge12 (M = Co, Pd, Tc, and Zr)
nanoclusters using the density functional theory. The outcomes are as
follows:
1. We can identify that the D6h symmetry hexagonal prism
structure is unique for germanium as well as silicon cage as described
by José M. Goicoechea in his research [58]. It can
be seen by figure 2, the HP, Ih, and HAP structure reach their maximum
stability when total valence electron in the system count 52-58
electrons. In this case TM atoms completely fall into the germanium
cage.
2. The magnitude of binding energy of the clusters indicate that the
doping of 4d transition metal Tc, and Zr gives most stable structure
rather than 3d transition metal Co atom.
3. The results show that doping of 4d transition metal like Tc, Zr, and
Pd have relatively large gap in compare to 3d transition metal Co. Here
we obtain 1.96eV [Tc@Ge12], 1.96eV
[Pd@Ge12], 1.86eV [Zr@Ge12], and
0.97eV [Co@Ge12] HOMO-LUMO gap for the most stable
clusters. The stability of these clusters can be defined using closed
shell electronic configuration and the contribution of π and σ bond.
4. Charge transfer mechanism shows that the Tc, Pd and Zr atoms play
role as a electron donor in the system whereas Co inclined to accept the
electrons.
5. PDOS calculation provides the information of localized “d”
electrons near the Fermi level. The electron density is mainly
distributed around the TM atoms. PdGe12 would be a good
candidate as the building block with high magnetic moment for cluster
assembly system.
So the overall conclusions suggest that the investigations of new hybrid
semiconductor clusters doped with different TM atoms are very useful in
electronic devices, laser application and sensors. The theoretical
modeling also show possibility of designing miniature devices using pure
and TM doped hybrid semiconductor clusters.