New examples of ternary rare-earth metal boride carbides containing finite boron-carbon chains: The crystal and electronic structure of RE{sub 15}B{sub 6}C{sub 20} (RE=Pr, Nd)
- Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, Postfach 800665, D-70569 Stuttgart (Germany)
- Arbeitsgruppe Neue Materialien, Universitaet Wien, Waehringerstrasse 42, A-1090 Wien (Austria)
- Sciences Chimiques de Rennes, UMR 6226 CNRS-Ecole Nationale Superieure de Chimie de Rennes-Universite de Rennes 1, Avenue du General Leclerc, F-35042 Rennes cedex (France)
The ternary rare-earth metal boride carbides RE{sub 15}B{sub 6}C{sub 20} (RE=Pr, Nd) were synthesized by co-melting the elements. They exist above 1270 K. Their crystal structures were determined from single-crystal X-ray diffraction data. Both crystallize in the space group P1-bar , Z=1, a=8.3431(8) A, b=9.2492(9) A, c=8.3581(8) A, {alpha}=84.72(1){sup o}, {beta}=89.68(1){sup o}, {gamma} =84.23(1){sup o} (R1=0.041 (wR2=0.10) for 3291 reflections with I{sub o}>2{sigma}(I{sub o})) for Pr{sub 15}B{sub 6}C{sub 20}, and a=8.284(1) A, b=9.228(1) A, c=8.309(1) A, {alpha}=84.74(1){sup o}, {beta}=89.68(1){sup o}, {gamma}=84.17(2){sup o} (R1=0.033 (wR2=0.049) for 2970 reflections with I{sub o}>2{sigma}(I{sub o})) for Nd{sub 15}B{sub 6}C{sub 20}. Their structure consists of a three-dimensional framework of rare-earth metal atoms resulting from the stacking of slightly corrugated and distorted square nets, leading to cavities filled with unprecedented B{sub 2}C{sub 4} finite chains, disordered C{sub 3} entities and isolated carbon atoms, respectively. Structural and theoretical analyses suggest the ionic formulation (RE{sup 3+}){sub 15}([B{sub 2}C{sub 4}]{sup 6-}){sub 3}([C{sub 3}]{sup 4-}){sub 2}(C{sup 4-}){sub 2}.11e. Accordingly, density functional theory calculations indicate that the compounds are metallic. Both structural arguments as well as energy calculations on different boron vs. carbon distributions in the B{sub 2}C{sub 4} chains support the presence of a CBCCBC unit. Pr{sub 15}B{sub 6}C{sub 18} exhibits antiferromagnetic order at T{sub N}=7.9 K, followed by a meta-magnetic transition above a critical external field B>0.03 T. On the other hand, Nd{sub 15}B{sub 6}C{sub 18} is a ferromagnet below T{sub C}{approx}40 K. - Graphical abstract: The ternary rare-earth metal boride carbides RE{sub 15}B{sub 6}C{sub 20} (RE=Pr, Nd) were synthesized by co-melting the elements. They exist above 1270 K. Their structure consists of a three-dimensional framework of rare-earth metal atoms resulting from the stacking of slightly corrugated and distorted square nets, leading to cavities filled with unprecedented B{sub 2}C{sub 4} finite chains, disordered C{sub 3} entities and isolated carbon atoms, respectively. Structural and theoretical analyses suggest the ionic formulation (RE{sup 3+}){sub 15}([B{sub 2}C{sub 4}]{sup 6-}){sub 3}([C{sub 3}]{sup 4-}){sub 2}(C{sup 4-}){sub 2} 11e. Pr{sub 15}B{sub 6}C{sub 18} exhibits antiferromagnetic order at T{sub N}=7.9 K, followed by a meta-magnetic transition above a critical external field B>0.03 T. On the other hand, Nd{sub 15}B{sub 6}C{sub 18} is ferromagnetic below T{sub C}{approx}40 K.
- OSTI ID:
- 21128388
- Journal Information:
- Journal of Solid State Chemistry, Vol. 181, Issue 8; Other Information: DOI: 10.1016/j.jssc.2008.04.003; PII: S0022-4596(08)00185-0; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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