Simulation models, based on an ionic description of closed-shell species and which incorporate many-body polarization effects, are derived for both yttrium and lanthanum aluminates using physically transparent mixing and scaling arguments. Three compositions $(20\%{\mathrm{Y}}_2{\mathrm{O}}_3/80\%{\mathrm{Al}}_2{\mathrm{O}}_3,$ $25\%{\mathrm{Y}}_2{\mathrm{O}}_3/75\%{\mathrm{Al}}_2{\mathrm{O}}_3,$ and $25\%{\mathrm{La}}_2{\mathrm{O}}_3/75\%{\mathrm{Al}}_2{\mathrm{O}}_3)$ are studied in detail. The models are validated by direct comparison with the recently determined x-ray and neutron diffraction patterns. The complementary nature of the two diffraction patterns is shown to be highly important for effective model validation. The success of the models in reproducing the experimental scattering patterns allows the breakdown into the partial structure factors, and the corresponding real-space functions, to be fully understood. Significant features in the total scattering functions are identified and attributed to specific ion spatial correlations in a manner not possible using the total scattering function information only. Subtle differences in the real-space structure as a function of composition are analyzed and discussed in relation to possible polyamorphic behavior.

• Received 11 August 2003

DOI:https://doi.org/10.1103/PhysRevB.69.054206