Optical constants and crystal chemical parameters of Sc2W3O12

Abstract The refractive indices of Sc 2 W 3 O 12 , measured at wavelengths of 435.8–643.8 nm, were used to calculate n a  = 1.7331, n b  = 1.7510, n c  = 1.7586 at λ  = 589.3 nm and n ∞ values at λ  = ∞ from a one-term Sellmeier equation. Mean refractive indices, 〈 n D 〉, and mean dispersion values, 〈 A 〉, are, respectively, 1.7475 and 110 × 10 −16  m 2 . Total electronic polarizabilities, α obs , were calculated from n ∞ and the Lorenz–Lorentz equation. The unusually large difference between the observed polarizability of 28.415 A 3 and the calculated total polarizability α T of 26.74 A 3 ( Δ  = +6.3%) is attributed to (1) a large M–O–W angle, and (2) a high degree of W 5 d –O 2 p and Sc n d –O 2 p hybridization, where n signifies unspecified Sc d orbitals.