Redetermination of the crystal structure of Si ( = Pr, Nd) from single-crystal X-ray diffraction data.

The crystal structures of praseodymium silicide (5/4), PrSi, and neodymium silicide (5/4), NdSi, were redetermined using high-quality single-crystal X-ray diffraction data. The previous structure reports of PrSi were only based on powder X-ray diffraction data [Smith (1967 ▸). 940-943; Yang (2002 ▸). , 189-194; Yang , (2003 ▸). , 146-153]. On the other hand, the structure of NdSi has been determined from powder data [neutron; Cadogan , (2002 ▸). , , 7191-7200] and X-ray [Smith (1967 ▸). 940-943; Yang (2002 ▸). , 189-194; Yang , (2003 ▸). , 146-153] and single-crystal data with isotropic atomic displacement parameters [Roger , (2006 ▸). , 73-84]. In addition, the anisotropic atomic displacement parameters for all atomic sites have been determined for the first time. These compounds are confirmed to have the tetra-gonal ZrSi-type structure (space group: 422), as reported previously (Smith , 1967 ▸). The structure is built up by distorted body-centered cubes consisting of Pr(Nd) atoms, which are linked to each other by edge-sharing to form a three-dimensional framework. This framework delimits zigzag channels in which the silicon dimers are situated.