Title: A Computational Study of Yttria-Stabilized Zirconia: I. Using Crystal Chemistry to Search for the Ground State on a Glassy Energy Landscape,
Abstract: Yttria-stabilized zirconia (YSZ), a ZrO2-Y2O3 solid solution that contains a
large population of oxygen vacancies, is widely used in energy and industrial
applications. Past computational studies correctly predicted the anion
diffusivity but not the cation diffusivity, which is important for material
processing and stability. One of the challenges lies in identifying a plausible
configuration akin to the ground state in a glassy landscape. This is unlikely
to come from random sampling of even a very large sample space, but the odds
are much improved by incorporating packing preferences revealed by a modest
sized configurational library established from empirical potential
calculations. Ab initio calculations corroborated these preferences, which
prove remarkably robust extending to the fifth cation-oxygen shell about 8
{\AA} away. Yet because of frustration there are still rampant violations of
packing preferences and charge neutrality in the ground state, and the approach
toward it bears a close analogy to glass relaxations. Fast relaxations proceed
by fast oxygen movement around cations, while slow relaxations require slow
cation diffusion. The latter is necessarily cooperative because of strong
coupling imposed by the long-range packing preferences.