Neutron Powder Diffraction on Ce¹¹B₂C₂ and Nd¹¹B₂C₂: A New Model for the Tetragonal Crystal Structure

抄録

Crystal structures of CeB₂C₂ and NdB₂C₂ were investigated by means of neutron powder diffraction using ¹¹B enriched samples. Diffraction patterns of Ce¹¹B₂C₂ and Nd¹¹B₂C₂ are very similar to each other, and Rietveld analyses reveal that the crystal structure belongs to a symmetry group of tetragonal P4/mbm, where the rare earth atoms occupy 2(a) sites and the B and C atoms occupy two 4(h) sites with different positional parameters. The newly determined structure differs from previously reported ones with P4/mbm and P{&overline; 4}2c mainly in the site positions occupied by the B and C atoms. The B and C atoms form network planes consisting of non-regular squares and octagons.