The influence of oxygen vacancy on the magnetism of Co-doped ZnO has been investigated by the first-principles calculations.It is suggested that oxygen vacancy and its location play crucial roles on the magnetic properties of Co-doped ZnO.The exchange coupling mechanism should account for the magnetism in Co-doped ZnO with oxygen vacancy and the oxygen vacancy is likely to be close to the Co atom.The oxygen vacancy (doping electrons) might be available for carrier mediation but is localized with a certain length and can strengthen the ferromagnetic exchange interaction between Co atoms.
The stability and local vibrational mode（LVM） of hydrogen related p-type AlN have been studied by firstprinciples calculations based on density functional theory.The stable and metastable microscopic geometries of group-Ⅱ（Be,Mg,Ca,Sr,Ba）-H complexes have been investigated.The calculated results indicate that BC‖ is the most stable configuration for isolated interstitial H+ and Be-H complexes,while it is ABn,⊥ for Mg-H,Ca-H,Sr-H and Ba-H complexes.Moreover,the vibrational frequencies and the values of k and |α| for the H atom with LVM are calculated. Here,the values of k and |α| are used to describe the parameters of the harmonic and anharmonic contributions,respectively. The calculated results indicate that the larger the size of the doped ion is,the shorter the N-H bond length is,and the larger the potential energy,the vibrational frequencies,the values of k and |α| are.This implies that the size of the doped ion has an important influence on the vibrational properties of H.
