Use the Clausius–Mossotti expression in Equation (8.13) and Table 8.2 to estimate permittivities of SnO² (rutile-type, P4₂/mnm, Z = 2, a = 4.74 Å, c = 3.19 Å), TiO₂ (rutile-type, a = 4.59 Å, c = 2.96 Å) and ZrO₂ (baddeleyite-type, P2₁/c, Z = 4, unit-cell volume = 141 Å). Does the Clausius–Mossotti equation give a reasonably accurate estimate for each compound when compared to the experimental values of εr given in Table 8.1? If not, what is the origin of the discrepancy?

Equation (8.13)

Table 8.2

Table 8.1

a= V 4 2 Er (+2) [CGSes : a in , V, in A]