High-pressure study on dioxolane silica sodalite (C3H6O2)(2)[Si12O24] - neutron and X-ray powder diffraction experiments

Neutron and X-ray high-pressure powder-diffraction experiments on silica so dalite with 1,3-dioxolane as a template molecule, (C3H6O2)(2)[Si12O24], wer e performed up to a maximum pressure of 2.7 GPa. A phase transition from th e fully expanded structure at ambient pressure, space group Im (3) over bar m, to the acentric space group I (4) over bar 3m was derived from the obse rved compression behaviour. A ferro-elastic phase transition appears at abo ut 1.2 GPa to the rhombohedral crystal system. From symmetry analysis and t he observed transition behaviour the space groups R3 or R3m are proposed fo r p > 1.2 GPa. (C) 2000 Elsevier Science Ltd. All rights reserved.