REVERSE MONTE CARLO SIMULATIONS OF THE NEUTRON- AND X-RAY DIFFUSE SCATTERING OF CUBIC STABILIZED ZIRCONIAS. Th. Proffen¹, T.R. Welberry¹, R.B. Neder², ¹Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia, ²Insitut für Kristallographie und Mineralogie, Universität München, Theresienstr. 41, 80333 München, Germany

A new approach to analyse the diffuse scattering of cubic stabilized zirconia is made by Reverse-Monte-Carlo (RMC) simulations. The RMC method applies random changes to a model structure and tries to optimize the agreement between the resulting diffraction pattern and the experimental data. The main features of the defect structure are given by oxygen vacancies introduced by the dopant material (e.g. CaO, Y₂O₃, MgO) and the relaxation of the oxygens and metals neighbouring these vacancies. Subsequently the simulations are carried out in four separate steps: ordering of the oxygen vacancies, ordering of the Zr and dopant metal ions and relaxation of the metal and metal ions. Calculations are still in progress. The RMC routines which allow to model occupational as well as displacive disorder were integrated in the program DISCUS [1]. They allow a simultaneous refinement of neutron- and x-ray data.

A successful RMC run will lead to one structure which produces a diffraction pattern in good agreement with the experimental data. The resulting structural features have to be discussed from a chemical point of view and are compared to the results of a recent study using the "modulated wave approach" and Monte Carlo simulations [2].

[1] DISCUS, (c) R.B.Neder & Th. Proffen, see http://rschp2.anu.edu.au:8080/proffen/discus/discus.html

[2] T.R. WELBERRY, R.L. WITHERS & S.C. MAYO (1995). J. Solid State Chem. 115, 43-54