Crystal structure of NaCl-type transition metal monocarbides MC (M = V, Ti, Nb, Ta, Hf, Zr), a neutron powder diffraction study

Crystal structure of NaCl-type transition metal monocarbides MC (M = V, Ti, Nb, Ta, Hf and Zr) has been investigated by Rietveld analysis of neutron powder diffraction data measured at 23 °C. The unit-cell parameter a of MC compounds increased with increasing of ionic radius of the metal species M. Structural change of the tantalum carbide TaC from 23 to 413 °C has been investigated by Rietveld analysis of in situ neutron diffraction data. The unit-cell parameter a, unit-cell volume and atomic displacement parameter of TaC increased with increasing of temperature. The thermal expansion coefficient of TaC was estimated to be (6.4 ± 0.3) × 10−6 °C−1.