Dibarium tricadmium bismuthide(-I,-III) oxide, Ba₂Cd_3−δBi₃O

Abstract

Key indicators: single-crystal X-ray study; T = 120 K; mean (Bi-Cd) = 0.001 Å; disorder in main residue; R factor = 0.032; wR factor = 0.073; data-to-parameter ratio = 17.3.Ba 2 Cd 2.13 Bi 3 O, a new bismuthide(-I,-III) oxide, crystallizes with a novel body-centered tetragonal structure (Pearson code tI36). The crystal structure contains eight crystallographically unique sites in the asymmetric unit, all on special positions. Two Ba, one Cd and two Bi atoms have site symmetry 4mm, the third Bi atom has mmm. and the O atom has 4m2 symmetry; the second Cd site (2mm. symmetry) is not fully occupied. The layered structure is complex and can be considered as an intergrowth of two types of slabs, viz. BaCdBiO with the ZrCuSiAs type and BaCd 2 Bi 2 with the CeMg 2 Si 2 type. Related literatureIsotypic compounds are not known; however, there are several compounds whose structures are based on fused CdBi 4 tetrahedral fragments, including BaCdBi 2 (Brechtel et al., 1981) (Cordier et al., 1982;Xia & Bobev, 2006b). The serendipitous discovery of the title compound was the result of a systematic study of the Ba-Cd-Bi system, inspired from the identification of Ba 3 Cd 2 Sb 4 (Saparov et al., 2008). The compound BaCdSbF (Saparov & Bobev, 2010) is an example of a structure that epitomizes the BaCdBiO slabs. Recently, the idea that intermetallic oxide-pnictides and fluoride-pnictides could be a widespread class of quaternary solids has been discussed on the examples of Ba 5 Cd 2 Sb 5 O x (0.5<x<0.7) and Ba 5 Cd 2 Sb 5 F (Saparov & Bobev, 2010). Theoretical considerations of non-classical electron-rich networks of the pnictogen elements is proved by Papoian & Hoffmann (2000). For standardization of the atomic coordinates, the program STRUCTURE-TIDY was used (Gelato & Parthé, 1987). For further information on structure types among intermetallic phases, we refer to Pearson's Handbook (Villars & Calvert, 1991). ExperimentalCrystal data

On the New Oxyarsenides Eu5Zn2As5O and Eu5Cd2As5O

“…A brief exposure to the atmosphere during the sealing of an ampoule or inadvertent reduction of alumina (crucible material) might be all the opportunity necessary for unintended oxygen to find its way into the reaction materials or products, resulting in an unplanned oxide phase. While they are infrequent discoveries in our lab, these uncommon oxygen-stabilized phases have been documented in several previous studies, such as Ca 4 Bi 2 O, Ba 2 Cd 3-δ Bi 3 O, Ba 5 Cd 2 Sb 5 O x (0.5 < x < 0.7), Eu 5 Cd 2 Sb 5 O, and Ba 5 Cd 2 Sb 4 O 2 [22][23][24][25][26]. This small group is expanded with the two title compounds presented herein.…”

Pentaeuropium dicadmium pentaantimonide oxide, Eu5Cd2Sb5O

“…2.6-2.7 Å from Eu, remained in the difference Fourier map. Unlike the case of Ba 2 Cd 3-δ Bi 3 O (Xia & Bobev, 2010), where the residual density lacked the typical oxoanion coordination and was modeled as a partially occupied Cd site, here the tetrahedral coordination by Eu matches very well the bonding requirements of O 2-. The distances are reasonable and the oxygen site was fully occupied, as verified by freeing the site occupation factor, which led to an occupancy factor of 1.05 (2).…”

“…For related antimonide fluorides and oxides [A 5 Cd 2 Sb 5 F (A = Sr, Ba, Eu); Ba 5 Cd 2 Sb 5 O x ], see: . For another related bismuthide oxide (Ba 2 Cd 2.13 Bi 3 O), see: Xia & Bobev (2010). For ionic and covalent radii, see: Shannon (1976); Pauling (1960).…”