A COMPUTATIONAL STUDY OF OXYGEN ORDERING IN YBA2CU3OZ AND ITS RELATION TO SUPERCONDUCTIVITY

An ab initio model to study oxygen ordering in the high temperature su perconductor YBa2Cu3Oz is presented. The phase diagram computed with t his model contains several ordered structures and is in excellent agre ement with the known experimental information. At high temperature, an orthorhombic structure transforms by a second order reaction into a t etragonal structure. At low temperature, a branching algorithm generat es an infinity of ordered structures all consisting of long O-Cu-O cha ins. By looking at the kinetic evolution of quenched samples in a Mont e Carlo simulation it was possible to clarify how annealing of the mat erial can influence its superconducting transition temperature.