10.1007/s11445-008-2019-x

Abstract

The processes of oxygen diffusion in La 2 -x Sr x CuO 4 -δ phases have been simulated for the first time by the molecular-dynamics method. Calculations were performed for the temperature range 300-2500 K. The behavior of the radial pair correlation functions, which characterize the degree of order of O1 ions in CuO 2 layers, indicates that O 2anions form a weakly correlated subsystem within a CuO 2 layer. To quantitatively confirm the conclusions about the predominantly two-dimensional character of ion transport and different mobilities of O1 and O2 particles in the cuprates under study, the pair oxygen diffusion coefficients in the La 2 − x Sr x CuO 4 -δ lattice were calculated. It is shown that oxygen diffusion occurs through the conventional hopping mechanism mainly in CuO 2 layers; correspondingly, the diffusion coefficient for equatorial ions (O1) exceeds that for apical oxygen anions (O2) by an order of magnitude. The motion of oxygen anions was traced at the microscopic level through analysis of the particle transport trajectories. It has been proven for the first time that diffusion of O1 ions in the ab plane in a nonstoichiometric LaSrCuO 3.61 sample occurs through jumps to the nearest position or along CuO 2 layers; in a more complicated way, it may occur through unoccupied O2 lattice sites.