COMPRESSION MECHANISM IN TRIOXANE SILICA SODALITE, [SI12O24]CENTER-DOT-2C3H6O3

Cubic silica sodalite with 1,3,5-trioxane template, [Si12O24] . 2 C3H6O3, a0 = 8.8349(1) angstrom, space group I43mBAR, Z = 1, was studied at room temperature and at elevated pressures up to 1.28 GPa with neutron powder diffraction. No deviations from cubic symmetry could be observed with increasing pressure. The linear bulk modulus of the compound was determined to be 132(7) GPa. Rietveld profile refinements revealed that the volume reduction under pressure is correlated with an increase of the cooperative tilting of the relatively rigid framework SiO4-tetrahedra. This suggests that the tilting is the principal component of the compression mechanism.