The structural, energetic, and electronic properties of stoichiometric and defective Li2O were studied theoretically. The reliability of the Perdew-Wang method in the framework of density functional theory, and of 2 DFT/Hartree-Fock hybrid methods (PW1PW and B3LYP), was examined by comparison of calculated and available experimental data.

Atom-centered orbitals and plane waves were used as basis functions for the crystalline orbitals. For most of the methods, good agreement with the experimental Li2O lattice parameter and cohesive energy was obtained. In accordance with experiment, an analysis of electronic properties showed that Li2O was a wide-gap insulator. Among the considered methods, the hybrid methods PW1PW and B3LYP gave the best agreement with experiment, for the band-gap. The formation of an isolated cation vacancy defect and an F center in Li2O was studied. The effect of local relaxation upon the calculated defect formation energies and the defect-induced changes of electronic properties were investigated and compared with available experimental results. The migration of a Li+ ion in bulk Li2O was investigated. The activation energy for the migration of a Li+ ion from its regular tetrahedral site to an adjacent cation vacancy was calculated; including the effect of local relaxation. The calculated activation barriers, 0.27 to 0.33eV, were in excellent agreement with experiment.

Theoretical Analysis of Structural, Energetic, Electronic and Defect Properties of Li2O. M.M.Islam, T.Bredow, C.Minot: Journal of Physical Chemistry B, 2006, 110[19], 9413-20