Aluminium, crystal structure

The melting and boiling points of the aluminium halides, in contrast to the boron compounds, are irregular. It might reasonably be expected that aluminium, being a more metallic element than boron, would form an ionic fluoride and indeed the fact that it remains solid until 1564 K. when it sublimes, would tend to confirm this, although it should not be concluded that the fluoride is, therefore, wholly ionic. The crystal structure is such that each aluminium has a coordination number of six, being surrounded by six fluoride ions. 

It is stable up to 2000 K and melts under pressure at 2500 K. The crystal structure of aluminium nitride resembles that of boron nitride and diamond, but unlike both of these it is rapidly and exothermically hydrolysed by cold water ... 

For preparing lakes, a solution of aluminium sulfate (or chloride) is mixed with sodium carbonate, forming fresh alumina Al(OH)3. The colorant is then added and adsorbed on the surface of alumina. Usually the content of colorant in the lake ranges from 10 to 40%." The product is filtered, washed with water, dried, and milled. The product is allowed to contain unreacted alumina but must not contain more than 0.5% HCl-insoluble matter and not more than 0.2 % ether-extractable matter. - Lakes are insoluble in most solvents used for pure dyes, and they have high opacity and better stability to light and heat. Lakes impart their color by dispersion of solid particles in the food. The coloring properties of lakes depend on particles, crystal structures, concentrations of dye, etc. 

Bailey, N. A., P.H. Bird, and M. G. H. Wallbridge Stereochemistry of 1 1 Adducts of Aluminium Compounds Crystal Structure of Aluminium Borohydride Trimethylamine. Chem. Comm. 7 965, 438. 

Palenih, G. ]. The Crystal Structure of the Aluminium Hydride-N,N,N N -Tetramethylethylenediamine Adduct. Acta Cryst. 17, 1573 (1964). 

Recently, reactions of dimeric [Me2Al(/x-NEt2)]2 with different tripodal ligands have been reported. Along with an Al(/x-0)2Al ring, two Al(/i-N)2Al motifs are noted in the core of the crystal structure of the tetra(aluminium)... 

In addition, Pauling and Sherman (222) had proposed a ring structure for the anion of aluminium tetrametaphosphate on the basis of a crystal structure determination. The triphosphate NaBP3Oi0 must, then, have the chain structure already proposed by Schwarz (263), for Rudy and Schloesser (250) showed that the acid corresponding to the triphosphate has three strongly and two weakly acidic OH groups with the weakly acidic groups... 

As is seen from the behaviour of the more sophisticated Heine-Abarenkov pseudopotential in Fig. 5.12, the first node q0 in aluminium lies just to the left of (2 / ) / and g = (2n/a)2, the magnitude of the reciprocal lattice vectors that determine the band gaps at L and X respectively. This explains both the positive value and the smallness of the Fourier component of the potential, which we deduced from the observed band gap in eqn (5.45). Taking the equilibrium lattice constant of aluminium to be a = 7.7 au and reading off from Fig. 5.12 that q0 at 0.8(4 / ), we find from eqn (5.57) that the Ashcroft empty core radius for aluminium is Re = 1.2 au. Thus, the ion core occupies only 6% of the bulk atomic volume. Nevertheless, we will find that its strong repulsive influence has a marked effect not only on the equilibrium bond length but also on the crystal structure adopted. 

Analyses of electron density distributions have enabled the positions of major elements of high atomic weights such as iron and other transition elements to be located relative to lighter elements such as magnesium and aluminium in mineral crystal structures. The widespread availability of automated X-ray dif-fractometry and least squares refinement programs have increased the availability of site occupancy data for transition metal ions in most contemporary crystal structure refinements. 

Bonamico, M. The Crystal Structure of an Aluminosiloxane containing Five-co-ordinated Aluminium. Chem. Commun. 1966, 135—136. 

Figure 9-59. The crystal structure of aluminium trichloride after Muller [111]. The dimeric unit with four-member ring is discernible. Copyright 1993 John Wiley Sons. Used by permission.

Aluminium molybdate, Al2(Mo04)3, is an important compound in catalyst technology. Although the crystal structure contains four equally populated inequivalent Al sites, an... 

Aluminium Hydrides.—K[AlMe3SiH3] decomposes to give K[AlMe3H]. The crystal structure of the latter shows that isolated tetrahedral anions are present, with r(Al—H) = 1.730(57), r(Al—C) = 1.995(6) A.352... 

---