Relations between composition and structural and stable properties of cubic zinc selenide-silicon core-shell nanowires (NWs) are studied by first principles calculation. The diameter is between 1.1 and 2.7 nm, and the direction of the NWs considered is . The lattice constants of the nanowires deviate from the Vegard’s law positively with compressed ZnSe core. Stability of the NWs is discussed by taking binding energy into account. Pure Si NWs show an increasing trend of binding energy as the diameter increases while ZnSe NWs do not. Further analysis shows that zinc blende ZnSe NWs might be unstable under small diameters and a phase transition to wurtzite structure would occur. Our findings might give some guidance for the application of ZnSe/Si core-shell NWs in photoelectronics.
Geometric optimizations and calculations of GdGa<sub>7</sub>N<sub>8</sub> 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<sub>7</sub>N<sub>8</sub> was found to be 7 <i>μ</i>B. And most of the magnetic moment was focused on the Gd atom owing to its half-filled <i>4f</i>-shell.