Hittorf s phosphorus

Bottom Structure of Hittorf s phosphorus consisting of the same kind of tubes, but joined to grids the tube shown in the center belongs to another grid than the remaining tubes. 

We know of only two examples of parallel 2D interpenetration involving nets other than (6,3) and (4,4). One is Hittorf s phosphorus, in which two 82-10 nets, composed entirely of phosphorus atoms, interpenetrate [15], The other example, considered in the next section, differs from all the other parallel interpenetrating cases in that the composite formed is a three-dimensional interlocked structure. 

Bismuth may be used in place of lead, but it dissolves only one-fifth as much phosphorus, and the crystals obtained are less pure. The metals appear to be held in solid soln. Only very minute quantities of Hittorf s phosphorus are obtained by sublimation. According to L. Troost and P. Hautefeuille, the same variety is formed when red phosphorus is heated under press, to 580°. The work of A. Pedler, J. W. Retgers, and D. L. Chapman shows that this variety differs from ordinary red phosphorus only in the size and development of the crystals. Fine-grained red phosphorus is scarlet phosphorus, while coarse-grained red phosphorus is metallic or violet phosphorus. A number of other allotropes have been reported, but many of them are the result of a misinterpretation of facts, or of an incomplete knowledge of facts. 

Violet phosphorus (Hittorf s phosphorus) is a complex three-dimensional polymer in which each P atom has a pyramidal arrangement of three bonds linking it to neighboring P atoms to form a series of interconnected tubes, as shown in Fig. 15.3.3. These tubes lie parallel to each other, forming double layers, and in the crystal stmcture one layer has its tubes packed at right angles to those in adjacent layers. 

Figure 12 Phosphorus units in the structures of (CuQgPu, (CuOgPu, and (CuI)2Pi4 as compared to Hittorf s phosphorus...

Fig. 14.3 (a) The tetrahedral P4 molecule found in white phosphorus, (b) Part of one of the chain-like arrays of atoms present in the infinite lattice of Hittorf s phosphorus the repeat unit contains 21 atoms, and atoms P and P" are equivalent atoms in adjacent chains, with chains connected through P -P" bonds, (c) Part of one layer of puckered six-membered rings present in black phosphorus and in the rhombohedral allotropes of arsenic, antimony and bismuth. 

A violet crystalline allotrope, monoclinic phosphorus, or Hittorf s phosphorus, after its discoverer, can be produced by a complicated thermal and electrolytic procedure. The structure is very complex, consisting of tubes of... 

Red phosphorus is made by heating the white form at 400° for several hours. As many as six modifications may exist, none of which is structurally characterized, with one possible exception, Red, crystalline, so-called Hittorf s phosphorus has been structurally characterized,4 but there is no evidence that this occurs in ordinary red phosphorus, though it may. It is made by a complex process involving slow heating in molten lead, followed by slow cooling. The structure is extremely complex, involving a criss-cross packing of infinite tubular chains of P atoms. 

CU2P3I2, that is, (CuI)8Pi2. Also, the compounds (CuI)3Pi2 and (CuI)2Pi4 with phosphorus strands similar to Hittorf s phosphorus have been reported.All of these structures can be considered as neutral phosphorus substructures that are embedded in a copper halide matrix. Some of the neutral phosphorus fragments are presented in Figure 12. As an example for the packing of the 1-D phosphorus units in the copper halide matrix, the structure of (Cul)2 Pi4 is... 

A further test of non-local corrections is provided by the isomers of Pjo (Fig. 5). MD/DF calculations with the LSD approximation [46] indicated that structure 5a, recognizable as a structural unit of the chains in Hittorf s phosphorus [48], was the most stable, while HF-based methods [52] favoured the Cj structure 5b by a small amount (less than 0.1 eV). Incorporation of the non-local modifications to ,<. changed the relative stability of the two isomers, with the Cj form now lying 0.1 eV lower. Some additional comments on gradient corrections to are given in Sect. 6. 

White phosphorus is manufactured by reaction 15.1, and heating this allotrope in an inert atmosphere at 540K produces red phosphorus. Several crystalline forms of red phosphorus exist, and all probably possess infinite lattices. Hittorf s phosphorus (also called violet phosphorus) is a well-characterized form of the red allotrope and its complicated structure is best described in terms of interlocking chains (Figure 15.3b). Non-bonded chains lie parallel to each other to give layers, and the chains in one layer lie at... 

The substitution of As for P in any compound with P-P linkages is possible, at least in principle. Amongst the simplest known examples are white phosphorus derivatives P4. As , the black phosphorus derivative AsP, AS2P and the mixed sulphides P4. tAS tS3 (Chapter 4.3). Grey arsenic and black phosphorus have been reported as forming limited solid solutions, but the composition P20AS is believed to consist of ordered chains of P atoms as in Hittorf s phosphorus. The As atoms occupy special positions which allow them to link these adjacent chains. 

Whereas single-crystalline flakes of black phosphorus can be grown from a bismuth solution [138], crystallization from liquid lead leads to red platy crystals of another modification, called Hittorf s phosphorus. Its monoclinic structure [137] (Cih—P2c, Z = 84, all atoms in 4g) consists of cage-like Pg and P9 groups which are linked alternately by pairs of P atoms to form tubes of pentagonal cross section. Parallel tubes form double layers in which tubes of different layers are approximately perpendicular (at 89.6°) to each other. In one layer, the tubes are parallel with [110], in the crossed layer, parallel with [iTO]. Each tube is /... 

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