Charge ordering and Na-vacancy ordering in Na0.75CoO2 are investigated using first-principles electronic structure methods within the generalized gradient approximation (GGA) and GGA+U approximations. We find that Na ordering is determined not only by a competition between different Na site energies and Na+-Na+ repulsion, but also by the Co4+-Na+ repulsion when charge localization occurs. We predict a ground-state structure for Na0.75CoO2 in good agreement with experimental transmission electron microscopy and neutron-diffraction data and find that Co3+Co4+ charge ordering is strongly coupled to the Na-vacancy ordering.
|Physical Review B - Condensed Matter and Materials Physics
|Published - Nov 1 2005
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics