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The crystal structure of silica sodalite, including possible locations for encapsulated ethylene glycol, was determined at room temperature by using a combined single-crystal X-ray and powder neutron diffraction analysis. Unit cell composition: Siij024-2C2H4(0H)2, , = 845, cubic, Im3m, a = 8.830 (1) Á (X-ray), a = 8.8273 (1) Á (neutron). These refinements reveal that the correct space group for silica sodalite is Im3m (rather than /43m) and, therefore, that the sodalite framework is fully expanded. At room temperature, each sodalite cage contains one ethylene glycol molecule which has a range of geometrical positions. Intramolecular distances for the ethylene glycol molecule are (X-ray) C-C 1.78 (4), C-0 1.30 (6) Á, (neutron) C-C 1.70 (3), C-O 1.25 (3) Á. The shortest distances (3.4 Á) between oxygens of the framework and molecule are consistent with weak hydrogen bonding. From the neutron diffraction data it was found that a sluggish phase change from cubic to lower symmetry occurs upon cooling below 200 K. At 10 K, silica sodalite appears to be monoclinic with approximate cell parameters a = 12.250 (8) Á, b = 12.471 (8) Á, c = 8.512 (6) Á, ß = 91.37 (6)°, based on an indexing of 12 peaks, but the precise symmetry is as yet unknown.

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Local structure of NaCl-type crystalline Ge2Sb2Te5 has been studied by the atomic pair distribution function analysis of pulsed neutron powder diffraction data. We have found the large displacement of germanium atoms in this crystalline phase. Usually, such a large lattice distortion has disadvantages for the electric conductivity. The electronic band structure, however, implies that this significant distortion in addition to the lattice defect at Na site reduces only thermal conductivity, while the highly ordered tellurium atoms at Cl site keep high electric conductivity.

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