A structural analysis of CaSO4 · 0.5H2O, a dehydration product of gypsum, has been carried out through the Rietveld method on Xray powder diffraction data. A dehydrated powder of synthetic gypsum has been charged inside a non hermetically sealed capillary in order to allow a slow rehydration. The starting material has been identified as anhydrite,s pace group P6222, cell parameters a = 6.9691(2)Å, c = 6.3033(2)Å. The final product of the rehydration of anhydrite is CaSO4 · 0.5H2O, space group I2 (unique axis b), cell parameters a = 12.0350(5)Å, b= 6.9294(3)Å, c = 12.6705(4)Å, = 90.266(3)°. The structure of the hemihydrate is strongly pseudotrigonal, space group P3121. The symmetry lowering arises from water molecules ordering inside the channels.
The monoclinic I2 structure of bassanite, calcium sulphate hemihydrate (CaSO4 • 0.5H2O) / Ballirano, Paolo; Maras, Adriana; Meloni, Simone; Caminiti, Ruggero. - In: EUROPEAN JOURNAL OF MINERALOGY. - ISSN 0935-1221. - STAMPA. - 13:5(2001), pp. 985-993. [10.1127/0935-1221/2001/0013/0985]
The monoclinic I2 structure of bassanite, calcium sulphate hemihydrate (CaSO4 • 0.5H2O)
BALLIRANO, Paolo;MARAS, Adriana;MELONI, Simone;CAMINITI, Ruggero
2001
Abstract
A structural analysis of CaSO4 · 0.5H2O, a dehydration product of gypsum, has been carried out through the Rietveld method on Xray powder diffraction data. A dehydrated powder of synthetic gypsum has been charged inside a non hermetically sealed capillary in order to allow a slow rehydration. The starting material has been identified as anhydrite,s pace group P6222, cell parameters a = 6.9691(2)Å, c = 6.3033(2)Å. The final product of the rehydration of anhydrite is CaSO4 · 0.5H2O, space group I2 (unique axis b), cell parameters a = 12.0350(5)Å, b= 6.9294(3)Å, c = 12.6705(4)Å, = 90.266(3)°. The structure of the hemihydrate is strongly pseudotrigonal, space group P3121. The symmetry lowering arises from water molecules ordering inside the channels.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.