Powder diagrams

Karfunkel H R, B Rohde, F J J Leusen, R J Gdanitz, emd G Rihs 1993. Continuous Similarity Measure Between Nonoverlapping X-ray Powder Diagrams of Different Crystal Modifications. Journal oj Computational Chemistry 14 1125-1135. 

The reports about the crystal structure of Mn(Et2cftc)2, determined by means of X-ray powder diagrams are contradictory. According to Fackler and Holah (18) this compound is isomorphous with Cu(Et2rftc)2, but Lahiry and Anand (44) state the complex to be isostructural with Ni(Et2 tc)2- EPR data (g = 1.92 and g = 4.11) and magnetic susceptibility measurements (4.1 BM at room temperature) show the compound to be the first Mn(II) complex with a quartet ground state (44). 

X-ray powder diagrams obtained by the Guinier method show the tris (O-ethyl dithiocarbonato) complexes of chro-mium(III), indium(III), cobalt(III), iron(III), arsenic(III), and antimony(III) to be isomorphous. Carrai and Gottardi have determined the structure of the arsenic(III)18 and anti-mony(III)19 complexes. Crystallographic data for the cobalt(III) and chromium(III) ethylxanthate complexes are given by Derenzini20 and Franzini and Schiaffino,21 respectively. 

A new method for the elucidation of crystal structure has recently been described [11]. The procedure based on energy minimization is even applicable to low-quality powder data and unindexable powder diagrams. It can be described by four steps ... 

Fig. 93 shows the reflection angles of the a-, (3-, and y-crystal modifications. The measurements were carried out on powder diagrams derived from X-ray diffraction spectra. 

Phthalocyanines exhibit high polymorphism, as well [7]. They are insoluble nano crystalline materials, which produce poor x-ray powder diagrams with high preferred orientation and have been intensely investigated by electron microscopy and diffraction [8]. From copper phthalocyanine (CuPc) (Fig.2) nine polymorphs (a, P, y, 5, s, n, p, (, a and R) are known, but only the most stable P phase could be solved by single crystal x-ray diffraction [9] (P2i/c a=14.628 A, b= 4.790 A, c= 19.07 A, b=120.93°). 

Fergusson et al. pointed out that the X-ray powder diagram of the product was characteristic of their solid solution phase II indicating y-sulfur structure and cyclic eight-membered molecules. Recently Weiss confirmed it by determining... 

No structure analyses on transition metal compounds NasMeFe have been performed yet, but recently Vollmer 316) indexed a powder diagram... 

In addition to the tetrafluorides already described in Peacock s 255) review, the compound Rup4 has been prepared in the meantime 149). The authors conclude from the x-ray powder diagram the lattice to be simple magnetic behaviour indicates linking of octahedra. 

The powder diagrams of the ternary mangan(III)-fluorides LiMnF4 [163) KMnF4 and RbMnF4 [166) could not be indexed yet. Possibly the Jahn-Teller distortion not only affects the MnFe --octahedra, but also the symmetry of the unit cells, which, at least in the case of the potassium-and rubidium-compounds, should be very similar to each other. 

The same structure with a Jahn-Teller distortion even more pronounced was observed in RbCuFs 8). It is therefore beyond doubt, that the remaining compounds of Cu + and Cr2+ crystallize in the KCuFg-structure type, even if x-ray powder diagrams do not prove this. The lattice constants of the fluorides belonging to this group — some of the chromium compounds have been prepared only recently by Vollmer 316) — are summarized in the following Table 26. 

Powder diagrams of polymetalates, 19 248 [PPh4][Cd(TIPT)3], 40 446-447 (PPhJLMnCrCox),], ferromagnetic ordering, 43 229-230... 

Figure X-ray powder diagrams of crystalline beta-cyclodextrin-hydrate and the cinnamon oil beta-cyclodextrin complex.

Tn the course of experimentation with formulations of silica, alumina, and A various alkali metal oxides in attempts to prepare new synthetic zeolites, a formulation containing cesium replacing some of the sodium in a typical faujasite preparation yielded a new crystalline zeolitic product which showed a typically cubic powder diagram having a body-centered pattern of... 

Powder diagrams of 7 A chamosites vary considerably. Brindley (1951) has shown that this could be explained by the presence of both orthogonal and monoclinic stacking of layers. These two types occur in varying proportions in different specimens though the orthogonal form generally predominates. 

X-ray diffraction (in crystalline polymers) Unoriented crystalline polymers show X-ray diffraction patterns, which resemble powder diagrams of low-molecular crystals, characterised by diffraction rings rather than by spots. As a result of orientation the rings contract into arcs and spots. From the azimuthal distribution of the intensity in the arcs the degree of orientation of the crystalline regions can be calculated (Kratky, 1941). 

The deformation of the lattice as a result of the mechanical working is seen from the broadening of the lines in the X-ray diffraction picture, which are narrow under normal circumstances (Debye-Scherrer or powder diagram). 

The ion [BgOi7] - may exist in Na4Ga4[BgOi7], for which only the powder diagram has been given... 

Taupin D., A Powder-Diagram Automatic-Indexing Routine, J. Appl. Cryst. (1973) 6 pp. 380-385. 

---