The structural and electronic properties of the CdS/ZnS core-shell nanowires (NWs) oriented along [001] direction have been investigated by means of the first-principles calculation. It is found that CdS core suffers from the compressive strain in the CdS-core/ZnS-shell NWs, and ZnS core is stretched in the ZnS-core/CdS-shell NWs. A thicker ZnS shell can improve the NWs' stability, and a thicker CdS shell would decrease their stability. For both CdS/ZnS core-shell NWs, the band gap decreases linearly with increasing the shell when the core size is fixed. However, when the diameter of NWs is fixed, CdS-core/ZnS-shell NWs with a thicker shell would have larger band gap. The results agree well with that of red-shift or blue-shift of the spectrum in experimental observations. The partial density of states indicates that the contribution to valence band maximum mainly comes from the S-3p state, and the contribution to conduction band minimum mainly comes from Cd-5s state for CdS-core/ZnS-shell NWs. Thus the electrons would be effectively confined in CdS core, and the holes tend to distribute over both the core and shell. It can be deduced that CdS-core/ZnS-shell NWs with a thicker shell may have larger mobility.
Geometric optimizations and calculations of GdGa 7 N 8 cluster were performed by a DMoL program using spin-polarized density functional theory (DFT). The binding energy, HOMO-LUMO gap, Mulliken charge and bonding characteristics were computed and analyzed. It is found that the Gadolinium substituting the Gallium would make the bonds between itself and neighboring atoms longer than that of the undoped cluster. The magnetic moment of GdGa 7 N 8 was found to be 7 μ B . And most of the magnetic moment was focused on the Gd atom owing to its half-filled 4f-shell.
The electronic properties of zincblende ZnSe/Si core-shell nanowires (NWs) with a diameter of 1.1–2.8 nm are calculated by means of the first principle calculation. Band gaps of both ZnSe-core/Si-shell and Si-core/ZnSe-shell NWs are much smaller than those of pure ZnSe or Si NWs. Band alignment analysis reveals that the small band gaps of ZnSe/Si core-shell NWs are caused by the interface state. Fixing the ZnSe core size and enlarging the Si shell would turn the NWs from intrinsic to p-type, then to metallic. However, Fixing the Si core and enlarging the ZnSe shell would not change the band gap significantly. The partial charge distribution diagram shows that the conduction band maximum (CBM) is confined in Si, while the valence band maximum (VBM) is mainly distributed around the interface. Our findings also show that the band gap and conductivity type of ZnSe/Si core-shell NWs can be tuned by the concentration and diameter of the core-shell material, respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.