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

Cubic silica sodalite with 1,3,5-trioxane template, [Si12O24] . 2 C3H6 O3, a0 = 8.8349(1) angstrom, space group I43mBAR, Z = 1, was studied a t room temperature and at elevated pressures up to 1.28 GPa with neutr on powder diffraction. No deviations from cubic symmetry could be obse rved with increasing pressure. The linear bulk modulus of the compound was determined to be 132(7) GPa. Rietveld profile refinements reveale d that the volume reduction under pressure is correlated with an incre ase of the cooperative tilting of the relatively rigid framework SiO4- tetrahedra. This suggests that the tilting is the principal component of the compression mechanism.