ABSTRACT
A study of the ternary Rh-Mn-Bi phase diagram revealed the existence of two new ternary bismuthides, viz. hexarhodium pentamanganese octadecabismuthide (Rh6Mn5Bi18) and rhodium manganese tribismuthide (RhMnBi3). Their crystal structures represent new structure types. Rh6Mn5Bi18, with a Wyckoff sequence a f2 g2 i5, crystallizes in the tetragonal system (space group P42/mnm; Pearson symbol tP58), and RhMnBi3, with a Wyckoff sequence a c g i q, crystallizes in the orthorhombic system (Cmmm; oS20). In the Rh6Mn5Bi18 structure, the transition metal atoms are linked into ribbon-like structural units aligned along the [001] direction, whereas planar sheets are formed in RhMnBi3. In both crystal structures, the units formed by the transition metal atoms are enveloped by Bi atoms, which themselves form a loosely bound network. The linkage results in a layer structure for RhMnBi3, while in the case of Rh6Mn5Bi18, a three-dimensional network is formed; the latter, however, contains several areas where Bi...Bi distances suggest van der Waals interactions. Both phases under discussion have analogous structural motifs.
ABSTRACT
The noncentrosymmetric space group P43m but a pseudocentric cubic crystal structure were reported for the compound Ni5.20Sn8.7Zn4.16Cu1.04 [Larsson et al. (1994). Acta Cryst. C50, 9-12]. The recently described Ni2Sn2Zn shows a closely related structure, although it is centrosymmetric and contains additional voids which are partially occupied. Therefore, a new refinement of Ni5.20Sn8.7Zn4.16Cu1.04 based on the originally published structure factors was performed. The results indicate that the structure can indeed be described in the centrosymmetric space group Pm3m; no justification for the absence of the inversion centre could be found within the accuracy of the available data. In comparison with Ni2Sn2Zn, slight but significant differences were confirmed; consequently, the two structures are topologically related but not isotypic.
ABSTRACT
Dinickel ditin zinc, Ni(2)Sn(2)Zn, crystallizes in the cubic space group Pm3m, with a lattice parameter of a = 8.845 (1) Å and with all atoms occupying special positions. The crystal structure exhibits pronounced similarities with that of the quaternary compound Ni(5.20)Sn(8.7)Zn(4.16)Cu(1.04). It shares structural features with other compounds in the Ni-Sn-Zn system, such as Ni(5)Sn(4)Zn and Ni(3)Sn(2).
ABSTRACT
Work on the ternary Ni-Sn-Zn phase diagram revealed the existence of the title compound pentanickel tetratin zinc, Ni(3.17)Sn(2.67)Zn(0.67) [Schmetterer et al. (2012). Intermetallics, doi:10.1016/j.intermet.2011.05.025]. It crystallizes in the Ni(5)Ga(3)Ge(2) structure type (orthorhombic, Cmcm) and is related to the InNi(2) type (hexagonal, P6(3)/mmc) of the neighbouring Ni(3)Sn(2) high-temperature (HT) phase, but is not a superstructure. The crystal structure was determined using single-crystal X-ray diffraction. Its homogeneity range was characterized using electron microprobe analysis. Phase analysis at various temperatures indicated that the phase decomposes between 1073 and 1173 K, where a more extended ternary solid solution of the Ni(3)Sn(2) HT phase was found instead.
