Ab initio molecular dynamics study of lithium diffusion in tetragonal Li7La3Zr2O12

Using ab initio density functional theory the thermally-stimulated migration of lithium ions in the garnet-type material Li7La3Zr2O12 is investigated. The methods of ab initio molecular dynamics have been applied to calculate the lithium ion self-diffusion coefficient and the diffusion barriers as function of lithium ion concentration. The concentration of lithium in the initial Li7La3Zr2O12 crystal unit cell is varied from 53 to 59 atoms, where 56 lithium atoms represent the stoichiometric concentration. Almost monotonous dependencies of the main characteristics on the number of lithium atoms N(Li) have been found, except for a non-monotonous peculiarity of the stoichiometric compound (N(Li) = 56). Finally, the influence of the unit cell volume change on lithium ion diffusion parameters as well as lithium ion hopping rates has been studied.