Z. Naturforsch. 2014,
69b, 289 – 293
doi:10.5560/ZNB.2014-3333
Different Structural Models of YB2C2 and GdB2C2 on the Basis of Single-Crystal X-Ray Data
Olaf
Reckeweg and
Francis J.
DiSalvo
Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301, USA
Received December 16, 2013 / published online March 17, 2014
Samples of YB2C2 and GdB2C2 were synthesized by arc-melting and subsequent annealing of the products. Single crystals of the title compounds were examined with single-crystal X-ray methods. Five different tetragonal unit cell settings from the literature (obtained on the basis of symmetry considerations) were used for the refinement of the crystal structure of YB2C2, but a converging refinement was only achieved for the structural model in the space group P4/mbm (no. 127, Z = 2) with a = 533.27(3) and c = 354.58(3) pm, without obvious inconsistencies. Nevertheless, the results for the five different unit cell settings are compared and discussed. A refinement of the crystal structure of
the isotypic compound GdB2C2 was also performed with the lattice parameters a = 537.46(6) and c = 364.98(11) pm. Neither EuB2C2 nor YbB2C2 were obtained by melting cold-pressed pellets with the nominal composition RE1.5B2C2 in an arc-furnace or an induction furnace, or by just heating the pellets in sealed Ta ampoules.
Key words: Yttrium, Gadolinium, Boride, Carbide, Structure Elucidation