title: Ionic conductivity of Li2B4O7.
abstract: The formation and mobility of Li point defects in Li(2)B(4)O(7) are investigated theoretically with periodic quantum chemical calculations. Calculated defect formation energies obtained with a density functional theory/Hartree-Fock hybrid method and with the Perdew-Wang density functional method are compared. The basis set effect is investigated by comparison of results obtained with atom-centered basis functions and plane waves. With both methods only a moderate relaxation is observed for the atoms surrounding the Li defect position. The defect-induced change of electronic properties is investigated by calculating the density of states for the stoichiometric and defective supercells. The activation energy for the movement of a Li(+) ion along the (001) direction is calculated. It is observed that Li(+) ion migrates through a one-dimensional channel formed by the five-vertex lithium-oxygen (LiO(5)) polyhedra. The calculated activation energies are in excellent accord with experiment.
authors.affiliation: Applied Centre for Structural and Synchrotron Studies, University of South Australia, Mawson Lakes Campus, Mawson Lakes, Adelaide, South Australia 5095, Australia.
authors.forename: Mazharul M
authors.initials: MM
authors.lastname: Islam
authors.forename: Thomas
authors.initials: T
authors.lastname: Bredow
authors.forename: Christian
authors.initials: C
authors.lastname: Minot