Theoretical Study on Structural Stability, Growth Behavior and Photoelectron Spectroscopy of Copper-Doped Germanium Clusters CuGen-/0 (n=4-13)

Studies on Cu-doped germanium clusters in the neutral and mono-anion states CuGen-/0 (n = 4-13) are carried out employing a double-hybrid density functional mPW2PLYP scheme. The global minimal structure, spectral property, HOMO-LUMO gap, and stability of CuGen-/0 (n = 4-13) were confirmed. The results showed that the global minimal structures of the anionic clusters are Cu-substituted for a Ge in the ground state of anionic Ge-n+1(-) with n <= 8, and Cu atom is encapsulated into germanium cages starting from n = 9. For neutral, it is also Cu-encapsulated into cage-like Ge framework with n >= 9. The spectra information including adiabatic electron affinity, vertical detachment energy and simulated photoelectron spectroscopy were presented. The HOMO-LUMO gap, atomization energy, and second energy difference for CuGen-/0 (n = 4-13) clusters along with NICS of CuGe12- were evaluated to examine the thermodynamic and chemical stability. The results revealed that anionic cluster CuGe12- with a high-symmetry endohedral I-h configuration possessed a perfect thermodynamic stability and chemical reactivity, making it possible as appropriate building block for new multi-functional semiconductor materials.