(1) A sample of calcia-stabilised zirconia is prepared by heating 85mol%ZrO2 with 15mol %CaO at 1600C. The material had a cubic unit cell with a lattice parameter, a, of 0.5144nm and a measured density of 5485kg m3. Calculate the theoretical density of the sample and hence determine whether interstitials or vacancies are more likely to be present in the structure. (The parent structure is fluorite (CaF2), in which each cubic unit cell contains 4 metal positions and 8 nonmetal positions, to give an overall composi. tion of MX2.)