Crystal structure of the high-pressure phase of the oxonitridosilicate chloride Ce4[Si4O3 + xN7 − x]Cl1 − xOx, x≃0.2

Friedrich, Alexandra; Haussühl, Eiken; Morgenroth, Wolfgang; Lieb, Alexandra; Winkler, Björn; Knorr, Karsten und Schnick, Wolfgang (2006): Crystal structure of the high-pressure phase of the oxonitridosilicate chloride Ce4[Si4O3 + xN7 − x]Cl1 − xOx, x≃0.2. In: Acta crystallographica B, Bd. 62, Nr. 2: S. 205-211

Abstract

The structural compression mechanism of Ce4[Si4O3 + xN7 − x]Cl1 − xOx, x≃ 0.2, was investigated by in situ single-crystal synchrotron X-ray diffraction at pressures of 3.0, 8.5 and 8.6 GPa using the diamond–anvil cell technique. On increasing pressure the low-pressure cubic structure first undergoes only minor structural changes. Between 8.5 and 8.6 GPa a first-order phase transition occurs, accompanied by a change of the single-crystal colour from light orange to dark red. The main structural mechanisms, leading to a volume reduction of about 5% at the phase transition, are an increase in and a rearrangement of the Ce coordination, the loss of the Ce2, Ce3 split position, and a bending of some of the inter-polyhedral Si—N—Si angles in the arrangement of the corner-sharing Si tetrahedra. The latter is responsible for the short c axis of the orthorhombic high-pressure structure compared with the cell parameter of the cubic low-pressure structure.

• Dokumententyp: Zeitschriftenartikel
• Publikationsform: Publisher's Version
• Keywords: nitridosilicate; compression mechanism; high pressure; phase transition
• Fakultät: Chemie und Pharmazie
• Themengebiete: 500 Naturwissenschaften und Mathematik > 540 Chemie
• ISSN: 0567-7408
• Sprache: Englisch