Compression behaviour of nitridocarbidosilicates M(2) Si(4)N(6)C M = Y, Ho, Er studied with X-ray diffraction and ab initio calculations

Friedrich, A., Knorr, Karsten, Winkler, B., Lieb, A., Hoppe, H. A., Schnick, W., Milman, V. and Hanfland, M. (2009) Compression behaviour of nitridocarbidosilicates M(2) Si(4)N(6)C M = Y, Ho, Er studied with X-ray diffraction and ab initio calculations Journal of Physics and Chemistry of Solids, 70 (1). pp. 97-106. DOI 10.1016/j.jpcs.2008.09.016.

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Abstract

The compressibilities of the nitridocarbidosilicates Ln(2)[Si(4)N(6)C], Ln = Ho, Er, were investigated by in situ powder synchrotron X-ray diffraction. Pressures up to 36 GPa were generated using the diamond-anvil cell technique. A fit of a third-order Birch-Murnaghan equation of state to the p-V data resulted in the bulk modulus B(0) = 162(2) GPa and its pressure derivative B' = 5.1(3) at V(0) = 605.1(2) angstrom(3) for Ho(2)[Si(4)N(6)C]. For Er(2)[Si(4)N(6)C] the values are B(0) = 163(5) GPa and B' = 4.5(6) at V(0) = 602.8(2) angstrom(3). Complementary data of the pressure dependence of this family of compounds were obtained by density functional theory based model calculations for Y(2)[Si(4)N(6)C]. An anomalous compression behaviour is predicted to occur between 8 and 12 GPa for Y(2)[Si(4)N(6)C]. The bulk modulus was obtained from an Eulerian strain versus normalized stress plot to be about 165 GPa, i.e., a value very similar to the bulk moduli obtained experimentally for Er(2)[Si(4)N(6)C] and Ho(2)[Si(4)N(6)C]. The anomaly in the pressure dependence of the cell parameters seems to be due to an increase in the coordination number of the two symmetrically independent Y cations. This increase of coordination is mainly achieved by a rotation of the Si(3)N(3)C tetrahedron. (C) 2008 Elsevier Ltd. All rights reserved.

Document Type: Article
Keywords: Inorganic compounds High pressure X-ray diffraction Ab initio calculations Equations of state crystal-structure pressure nitridosilicates luminescence fluorescence zeolites nitride
Research affiliation: Kiel University
DOI etc.: 10.1016/j.jpcs.2008.09.016
ISSN: 0022-3697
Date Deposited: 22 Dec 2011 05:56
Last Modified: 08 Oct 2012 10:09
URI: http://eprints.uni-kiel.de/id/eprint/15775

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