Magnetism in stoichiometric and off-stoichiometric MnO clusters: Insights from {\it ab initio} theory

摘要

We study the composition dependent evolution of geometric and magneticstructures of MnO clusters within density functional theory. A systematic andextensive search through the potential energy surface is performed to identifythe correct ground state, and significant isomers. We find that the magneticstructures in these MnO clusters are complex, which has been explained usingthe intrinsic electronic structure of the cluster, and analyzed using modelHamiltonian with parameters obtained from maximally localized Wannierfunctions. The calculated vertical displacement energies of off-stoichiometricMnO clusters compare well with the recent experimental results. Interestingly,the charged state of the cluster strongly influences the geometry and themagnetic structure of the cluster, which are very different from thecorresponding neutral counterpart. Further, the importance of electroncorrelation in describing simple Mn-dimer and MnO clusters has been discussedwithin Hubbard model and hybrid exchange-correlation functional.