The high-temperature (β) modification of Y 4C 7 with Lu 4C 7 type and Dy 3C 4 with Sc 3C 4 type structure

Abstract

A new modification of Y 4C 7 has been prepared by arc-melting of the elemental components and subsequent annealing at 1300°C. Its crystal structure was refined from X-ray powder diffractometer data: P2 1/ c, a=372.6(1) pm, b=1369.2(2) pm, c=652.7(1) pm, β=103.04(1)°, Z=2, R=0.027 for 341 structure factors and 15 positional parameters. The C–C distances in the propadienyl anion are 125(3) and 132(3) pm in good agreement with the average C–C distance of 132 pm found in the structures of the carbides β-Ho 4C 7 and Lu 4C 7. The new carbide Dy 3C 4 has a tetragonal Sc 3C 4 type structure with the lattice constants a=808.4(1) pm and c=1588.1(3) pm.