Bismuth crystal structure

The radius of the second cation in known MuNbOFs, MU2Nb03F3 and Mul2Nb05F compounds containing bi- and trivalent metals, is usually similar to that of niobium s ionic radius. Such compounds cannot be considered as having an island-type structure and will be discussed later on. Only bismuth-containing compounds (Bi3+) display the presence of different cationic sublattices in their crystal structure. 

Fig. 28 shows the crystal structure of Bi2Nb05F with a space group of I4/mmm - D. Bismuth ions, along with anions, form Bi202 type Bi2(0,F)2... 

This bismuth-III structure is also observed for antimony from 10 to 28 GPa and for bismuth from 2.8 to 8 GPa. At even higher pressures antimony and bismuth adopt the body-centered cubic packing of spheres which is typical for metals. Bi-III has a peculiar incommensurate composite crystal structure. It can be described by two intergrown partial structures that are not compatible metrically with one another (Fig. 11.11). The partial structure 1 consists of square antiprisms which share faces along c and which are connected by tetrahedral building blocks. The partial structure 2 forms linear chains of atoms that run along c in the midst of the square antiprisms. In addition, to compensate for the... 

Fig. 20. X-ray crystal structure of the dimer [Bi2(cit)2]2, a possible constituent of bismuth antiulcer compounds. An additional bridging O from a neighboring unit is also shown bonded to Bi(III). Note that asymmetry in the coordination sphere due to the lone pair on the metal (cit = C(0)(C02)(CH2C02)2). Adapted from (452).

Working first with Polanyi, Weissenberg, and Brill, and later as the leader of the Textile Chemistry Section, Mark successively published papers on the crystal structures of hexamethylenetetramine, pentaerythritol, zinc salts, tin, urea, tin salts, triphenylmethane, bismuth, graphite, sulfur, oxalic acid, acetaldehyde, ammonia, ethane, diborane, carbon dioxide, and some aluminum silicates. Each paper showed his and the laboratory s increasing sophistication in the technique of X-ray diffraction. Their work over the period broadened to include contributions to the theories of atomic and molecular structure and X-ray scattering theory. A number of his papers were particularly notable including his work with Polanyi on the structure of white tin ( 3, 4 ), E. Wigner on the structure of rhombic sulfur (5), and E. Pohland on the low temperature crystal structure of ammonia and carbon dioxide (6, 7). The Mark-Szilard effect, a classical component of X-ray physics, was a result of his collaboration with Leo Szilard (8). And his work with E. A. Hauser (9, 10, 11) on rubber and J. R. 

The structure of white tin had been subjected to investigation first by Bijl and Kolkmeijer in 1918, who reported an incorrect structure. In 1923 Mark and Polanyi carried out a second investigation, and found the correct structure for this tetragonal crystal, a structure involving no variable parameters. In 1924 Mark and Hassel reported the results of their reinvestigation of the structure of bismuth, whose structure had been determined in 1921 by R. W. James, in Manchester, who assigned the value 0.232 + 0.004 to the variable parameter. Hassel and Mark verified the James structure, with the parameter equal to 0.236 + 0.003. The presently accepted value for the parameter is 0.2339. 

Crystal structures of the bismuth molybdate and of the mixed iron and cobalt solid solution molybdate samples were controlled by X-ray diffraction (10). The chemical compositions of the samples were determined by atomic absorption and their surface areas measured by nitrogen adsorption using the BET method. 

In the latter, the valency angles must be about 100°, so the layers cannot be flat. Their shape is obtained if, in Figure 38, the atoms shown with the clear circles are displaced somewhat below the plane of the paper and the shaded ones similarly, above it. If the layers formed in this way are then arranged on top of one another, the crystal structure of the elements arsenic, antimony and bismuth are obtained in their normal forms in which they have metallic properties. There also exists a modification of phosphorus with a similar structure. In addition, there are other forms of arsenic and antimony, the properties of which correspond to those of yellow phosphorus these forms contain molecules p As4 and Sb4. 

The ligand 3,4,5,6-tetrahydropyrimidine-2(l//)-thione (THPT) forms an S-bonded complex, BiCl3(THPT)3.225 The crystal structure (81) shows a fac octahedron. Interestingly, with bismuth perchlorate Bi(C104)3(THPT)5 is formed. 

Table 30 Some Crystal Structure Data for the Bismuth Halides...

Tetraethylammonium tetrakis(tetracarbonylferrio)bismuthate(3 — ), [Et4N]3-[BiFe4(CO)i6], is a green, oxygen-sensitive, crystalline solid whose crystal structure has been reported.2, 3 It is soluble in acetonitrile, but is insoluble in... 

Tetraethylammonium tetrakis(tetracarbonylferrio)antimonate(3 — ), [Et4N]3-[SbFe4(CO)16], is a red, powdery solid that may be stored indefinitely under nitrogen. The crystal structure has been reported and is isomorphous to the bismuth analogue.4 The characteristic IR bands are found at (MeCN, cm-1) 1971, 1910, and 1882. A maximum is observed in the visible region of the absorption spectrum (MeCN) at 480 nm (e, 2800). 

---