Internal Motion and Its Pressure Dependence in FeSiF6· 6H2O

Abstract

Both wideline and pulsed NMR techniques have been used to examine internal motion in FeSiF6· 6H2O. At room temperature and pressure the fluorine-fluorine contribution to the 19F second moment is 0.38± 0.06 G2 and indicates rapid reorientation of the SiF6− − group. The application of pressure slows the internal motion such that rigid lattice values of the 19F second moment are obtained above 50 kbar. Analysis of the second moment within the transition region allows calculation of an activation volume which is 2.4± 0.4% of the molar volume.