First-principles study on mixed SimNn (m + n = 2–9) clusters

The structures and stabilities of the mixed SimNn (m + n = 2–9) clusters have been investigated systematically by using Amsterdam Density Functional (ADF) program with TZ2P basis set in conjunction with self-consistent field (SCF). In the silicon–nitrogen binary cluster system, their structures transfer gradually from the three-dimensional structures of Si-rich clusters into the like-planar or like-linear structures of N-rich clusters. Near m = n stoichiometry, the lowest energy structures have higher stability. They usually feature a strong alternation of Si and N atoms. In addition, some N dimers and one small isomer can be observed in N-rich clusters. The binding energy between the N dimers and the small isomer is less than 0.02 eV. The most stable structures for pure Nn clusters with odd atom number also contain one N trimer besides some N dimers. A series of meta-stable like-zigzag linear structures in the pure Nn clusters have been also studied. The investigation on magnetism for the mixed clusters indicates that only SiN2 cluster presents the magnetic moment of 2.0μB.