Theoretical studies on the spin Hamiltonian parameters and local environment of Mn2+ in ZnO nanocrystal and bulk

By employing the perturbation calculations, the spin Hamiltonian parameters (SHPs) and local structures are uniformly explored for Mn2+ in the ZnO nanocrystal and bulk. The EPR spectra are satisfactorily explained for both the systems, and the defect structure information is obtained, i.e., the substitutional impurity Mn2+ may undergo the axial displacements of 0.036 and 0.042 Å away from the oxygen triangles along the C3 axis in the ZnO nanocrystal and bulk, respectively. The similar SHPs for Mn2+ in the nanocrystal and bulk can be illustrated as the approximately identical covalency (equal covalency factor N) as well as the smaller axial displacement, the stronger crystal-field (CF) interactions (larger cubic CF parameter Dq) and Mn2+ 3d-3s orbital admixture (larger core polarization constant κ) in the former.