Structure Study of ZnO:Eu with the Supercell Method
One of the interests on the study of doped materials with rare earths in their bulk or nanoscale size is owing to the enhancement of the intensity of light in their photoluminescence when a lanthanide exists in a receptor material, as ZnO in our case. Until now, one of the most useful theories for calculations of electronic properties in molecular and solid state systems is the Density Functional Theory (DFT), which is not capable to manage well the presence of high localized electrons, as in lanthanide compounds in general and the doped case in particular. We propose to study these materials with super cell model using some correction to the standard calculations. For this goal, we employ the WIEN2k  code using the LDA+U approximation to take into account the strong correlation of the f electrons coming from the lanthanide. We emphasise the study of deformation due to the presence of Eu ion in the structure of host material, optimizing the position of neighboring Oxygen atoms. This deformation has been related to Kondo Resonance  appearing around the Fermi Energy of the compound, due to hybridization  among the f electrons from rare earth and neighboring oxygen levels.
Velumani S., R. Asomoza and Umapada Pal
A. Blanca-Romero et al., "Structure Study of ZnO:Eu with the Supercell Method", Journal of Nano Research, Vol. 9, pp. 25-30, 2010