Crystal Structures of the Tetragonal Ceria-Zirconia Solid Solutions CexZr1-xO2 through First Principles Calculations (0 ≤ x ≤ 1)

Crystal structures of metastable tetragonal CexZr1-xO2 have been studied through first principles calculations (0 <= x <= 1). Unit-cell parameters a, c, and atomic coordinates of 24 atoms were optimized for all the occupational configurations of Ce and Zr atoms by using the constraints for cell parameters: a = b and alpha = beta = gamma = 90 degrees. Axial ratio and oxygen displacement from the regular position of the optimized structures of ground states decrease with increasing CeO2 content, which is consistent with diffraction experiments in the literature, The tetragonal (t '') form with axial ratio of unity is strongly suggested to be stable in Ce0.875Zr0.125O2, compared with the tetragonal (t') form with axial ratio larger than unity and the cubic phase. This work also demonstrates that the ground state of CexZr1-xO2 (x <= 0.75) is the t' form, The phase stability of the t' and t '' forms are discussed by comparing the ground states with experimental data in the literature.