Octahydridosilasesquioxane determined by neutron diffraction

Abstract

The structure of H 8 Si 8 O 12 has been determined by neutron diffraction at 29 K and compared with X-ray determinations at 9.5 and 100 K. There are only small geometrical differences, but it can be concluded that the deviation from the ideal molecular symmetry, O h (m3m), increases with decreasing temperature and that the large vibration amplitudes for the 0 atoms observed in the X-ray analyses are also present in the neutron structure. Static disorder of the O atoms is excluded. The molecular deformation is caused by the rigid HSiO 3 tetrahedra performing a cooperative torsional movement inducing vibrational deformations of the flexible Si− O−Si angles