| Popis: |
Potassium-rich nenadkevichite, Na 0.6 K 1.5 {(Nb 0.6 Ti 0.4 )(Nb 0.5 Ti 0.5 )[Si 4 O 12 ](O,OH) 2 }.1.6H 2 O, M = 582.9, monoclinic, space group Cm, a = 14.692(4), b = 14.164(4), c = 7.859(3) A, β = 117.87(2)°, V = 1445.7(1) A 3 , Z = 4, ρ c = 2.67 g/cm 3 , λ(MoKα) = 0.71073 A, μ = 22.16 cm −1 , dimensions (mm) 0.2 × 0.3 × 0.4, F(000) = 1120.32, room temperature, R = 0.055 for 1443 reflections with |F| > 3σ(F), twinned crystal, the twining index n = 2. The crystal structure, like the other members of the labuntsovite nenadkevichite group, contains columns formed by (Nb,Ti)-octahedra with shared trans-vertices. The octahedral columns are linked by tetrahedral four-membered rings [Si 4 O 12 ]. The statistically distributed K, Na-ions and water molecules are located in the channels of the mixed framework |
