Abstract
Rietveld refinements using X-ray powder-diffraction data of coronadite samples from Morocco (Pb1.06Ba0.10Mn7.7V0.20Al0.08O16) and Australia (Pb1.40Mn7.9Al0.05Zn0.05O16 · 1.55H2O) in space group I2/m, a = 9.938(2) Å, b = 2.8678(5) Å, c = 9.834(2) Å, β = 90.39(2)° (Morocco) and a = 9.913(1) Å, b = 2.8652(4) Å, c = 9.843(1) Å, β = 90.20(1)° (Australia) confirm the basic hollandite structure. The Pb is displaced about 0.60 Å along the tunnels from the special position at (0, 0, 0). This displacement increases intercation distances in the tunnels, allowing up to two-thirds of the tunnel sites to be occupied by Pb cations
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