Calculated x-ray powder patterns

We believe that though the calculated x-ray powder patterns are only first approximations, the strategy of building related framework models, calculating the x-ray powder patterns, and then using them for screening to identify specimens worthy of more detailed examination, is an efficient and useful approach which may be extended to other zeolite systems. 

The behaviour of the zwitterion towards NH3 is similar the neutral system quantitatively transforms into the hydrated ammonium salt [Com(r 5-C5H4COO)2] [NH4] 3H20 upon 5 min of exposure to vapour of 30% aqueous ammonia. Single crystals of the ammonium salt for X-ray structure determination can be obtained if the reaction of the zwitterions with ammonia is carried out in aqueous solution. As in the case of the chloride salt, formation of [Com(q5-C5H4COO)2][NH4] 3H20 in the heterogeneous reaction is assessed by comparison of the observed and calculated X-ray powder patterns. Absorption of ammonia is also fully reversible upon... 

Table 1. Structural Parameters and Calculated X-ray Powder Diffraction Pattern of Nd186Ce016CuO4 (Structural Parameter From ref. 25)...

The intent of this chapter is twofold. One is to give brief structural descriptions of many of the copper-oxide superconductors. For in-depth information, the reader is referred to the original publications. The second is to provide detailed crystallographic information (lattice constants, positional and thermal parameters, space groups, etc.), and compositional data on many of the superconductors discussed. Also, calculated x-ray powder diffraction patterns for these same compounds are tabulated. It is hoped that such information will prove useful to the superconductivity researcher. 

Tables 1 through 7 giving positional and isotropic thermal parameters for most of the compounds discussed in this chapter. These data are taken, for the most part, from the literature, but, for a few materials that have not been structurally characterized, calculated positions are given. The tables also include lattice constants, space groups, and compositional data. Table 8 gives calculated x-ray powder diffraction information (26 (Cu), d-spacing, hkl, and intensity) for the same oxide compounds. In regard to the diffraction patterns, it should be remembered that preferred orientation and absorption effects, and cation substitutions will make the experimentally observed intensities differ from the calculated ones. Additional information on the crystal structures of high-Tc oxides can be found in a recent review (48).

Table 8. Calculated x-ray powder diffraction patterns for the compounds in Tables 1 through 7. Patterns were calculated using LAZY PULVERIX (47) with copper radiation (X = 1.5418 A). Not all lines are given. Calculated intensities less than 1 are not included.

Fortran Program for Calculating X-Ray Powder Diffraction Patterns , UCRL-50264, Lawrence Radiation Lab, Livermore (1967) 10) J.V. 

X-ray powder patterns were calculated (13) for the four idealized structures, using the atomic parameters and cell dimensions determined by Meier (11), Although these parameters will be slightly different for the four structures, they have been used here as a first approximation. 

X-ray powder patterns determined in the present studies and from the literature are summarized in Table III. The observed patterns for Zeolon 100 Na and Zeolon 100 H (synthetic sodium and hydrogen large port mordenites) arc in excellent agreement with the calculated patterns for the Cmcm structure. 

Smith, D. K., A Revised Program for Calculating X-ray Powder Diffraction Patterns, Lawrence Radiation Laboratory, University of California, Livermore, Rept. UCRL-50264 (June 12, 1967). 

The structure of A-type starch crystals was derived through the joint use of electron diffraction of single crystals, x-ray powder patterns decomposed into individual peaks, x-ray fiber diffraction data and extensive molecular modeling32 (Figure 5.5). The density calculated for the crystalline region (d = 1.48) is reasonably close to the observed density, and indicates that there are 12 glucosyl units and 4 water molecules in the unit cell. Intra- and inter-molecular energy calculations showed that... 

Fig. 10 a Observed, calculated and difference X-ray powder diffraction profiles of Li3Ru04. b Theoretical X-ray powder pattern calculated using the structure shown in Fig. 9a [2]. Reproduced by permission of The Royal Society of Chemistry...

Calculated X-ray powder diffraction patterns for tricalcium silicate and clinker phases... 

According to Drits (private communication, 1979) structure-factor calculations for the hM reflections of tochilinite I show that the reflections with k = 5n and k = 6n ought to be among the strongest reflections because of the subperiodidties of metal atoms in the two component structures. On the X-ray powder patterns and rotation photographs... 

Fig. 9.3 Calculated X-ray powder diffraction patterns for the (a) orthorhombic and (b) monoclinic polymorphs of TNT (from Gallagher and Sherwood 1996, with permission). The experimental powder patterns reported by Connick et al. (1969) are also hsted in the PDF.

Figure 20. Calculated X-ray scattering patterns for various types and sizes of Pt nanocrystallites. Top left 3.5 nm (a) sphalerite (b) wurtzite (c) wurtzite with one stacking fault (d) experimental powder spectmm with ca. 3.5.nm avg. crystallites. Top right Experimental powder diffraction pattern of ca. 8.0 nm crystallites (dotted line) compared to (a) spherical and (b) prolate particles (solid line) Center (a) progression of habits of cuboctahedral shapes of nanocrystals, (b) change in shape as 111 faces increase and 100 decrease, (c) decahedron and icosahedron multiply twiimed forms. Bottom left to right three successive sizes of cuboctahedral nanociystallites three successive sizes of decahedral nanociystallites three successive sizes of icosahedral nanocrystallites. From Zanchet et al. (2000), used with permission of Wiley-VCH.

POWDER CELL a program for the representation and manipulation of crystal structures and calculation of the resulting X ray powder patterns., W. Kraus and G. Nolze, J. Appl. Crystallogr., 1996, 29, 301 303... 

The InsS4 crystals have been found to form in different shapes depending on the thermal pre-history. The X-ray powder patterns of the reaction batches were identical, however, and all the crystals are red and transparent. The cubic unit cell dimension is a = 12.35 A, and the cell contains eight formula units of In5S4. The structure is of a new type.8 The calculated density is 4.95 g/L compared with the observed density of 4.87 g/L. The magnetic susceptibility was found to be —1.9 x 10-4 cm3mole 1. 

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