Phase Transitions of Silicasodalite under High Pressure-Single Crystal Studies with Synchrotron Radiation

The compressibilities of ethylenglycol and ethanolamin silica sodalite (EGS-SOD and EAS-SOD) have been measured up to 3. 1 and 3. 2 GPa, respectively. Both compounds show extraordinarily high compressibilities, from a fit to a Birch Murnaghan equation of state the bulk moduli and pressure derivatives calculate to K=8. 3 (5) GPa, K'=8 (1) and K=9. 7 (7) GPa, K'=3. 8 (7). EGS-SOD shows three phase transitions to a monoclinic and two triclinic high pressure phases in the pressure range investigated. These phase transitions are completely reversible and no twinning has been observed while passing the transition pressures. The structures of the monoclinic and of the 1st triclinic high pressure phase have been solved on the basis of intensity data collected with synchrotron radiation. Whereas the ethylenglycol guest molecules are dynamically disordered under room conditions, they adopt an ordered arrangement in the 2nd high pressure phase. Structure refmements of EASSOD again reveal a triclinic high pressure phase at 1. 1 GPa