Simulation of ion transport in layered cuprate La₂SrCu₂O₆

Abstract

Oxygen diffusion in layered cuprate La₂SrCu₂O₆ has been simulated by the molecular dynamics method in the temperature range of 300–2500 K. The lattice is found to transform at temperatures above 1550 K; this transformation is accompanied by a change in the pair correlation functions. The abrupt change in the oxygen diffusion coefficient in the range of 1500–1550 K may indicate the presence of a phase transition to the superionic state. The motion of oxygen anions could be traced at the microscopic level. It has been proven for the first time that the La₂SrCu₂O₆ crystal lattice allows, along with displacements of O1 ions within the CuO₂ layer, their migration from the crystallographic positions to the intermediate unoccupied O3 positions. The motion of O2 anions is also fairly complicated: they move not only in their layer over the O2 positions but they also jump to the neighboring layer to occupy the O1 positions. The oxygen diffusion coefficient in layered cuprate La₂SrCu₂O₆ exceeds that in cuprates with perovskite structure and structure of the K₂NiF₄ type (at the same temperatures), which indicates that this material has good prospects for electrodes with mixed ionic-electronic conductivity.