JCPDS data file

X-Ray powder diffraction patterns are catalogued in the JCPDS data file,7 and can be used to identify crystalline solids, either as pure phases or as mixtures. Again, both the positions and the relative intensities of the features are important in interpretation of powder diffraction patterns, although it should be borne in mind that diffraction peak heights in the readout from the photon counter are somewhat dependent on particle size. For example, a solid deposit accumulating in a heat exchanger can be quickly identified from its X-ray powder diffraction pattern, and its source or mechanism of formation may be deduced—for instance, is it a corrosion product (if so, what is it, and where does it come from) or a contaminant introduced with the feedwater ... 

Phase identification of the catalysts was carried out by powder X-ray diffractometiy using a Siemens D501 computer-controlled difftactometer, with monochromatized Cu Ka radiation. Patterns were registered in steps of 0.08°, in the angular range 20 to 65° 26, with integration times of 5 seconds per step. The sanq>les were dusted through a deve onto the holder surfrce to reduce preferred orientation. The obtained patterns were conq>ared with JCPDS data files. 

Table 5.30 Tools for mineral identification by employing JCPDS data file (1998)...

Based on the X-ray diflEractograms of both these ashes (OLA and OHA) and their activated residues, as depicted in Fig. 5.21a, b, results obtained after peak matching with the help of JCPDS data files [35] have been listed in Table 5.38. It can be deciphered from these results that the ALA samples contain fewer crystals of zeolite Na-Pl (refer Fig. 5.6). Most specifically, the residue ALA6 exhibits the presence of the zeolite Na-Pl for M < and Hydroxy-sodalite for M > [23]. On the other hand. Fig. 5.4b exhibits the peaks corresponding to the zeolites Na-Pl and Hydroxy-sodalite in the residue, AHA2. However, as listed in Tables 5.4 and 5.5, the zeolites, Cancrinite and Analcime, were also found in the residue AHA6. This... 

Table 6.1 Mineral phase identification by JCPDS data files and quantification by Rietveld refinement method...

Those who wish to access a remote computer by teletype may lease from the JCPDS the Diffraction Data Tele-Search called IdTS, which provides access to the magnetic-tape version of the data file. 

XRD spectra were measured on a Kristalloflex Siemens D5000 diffractometer using the Cu Ka radiation (k = 154.18 pm). Samples were analysed after deposition on a quartz monocrystal sample-holder (Siemens). The measurements have been made in the 20 range 5 - 80° by steps of 0.02°. The crystalline phases were identified by reference to the powder diffraction data files (JCPDS-ICDD). 

JCPDS, Joint Commission of Powder Diffraction Data Files, PCPDF WIN, Version 1.30, Pennsylvania, PA, 1997. 

Figure 9. X-ray intensity as a function of 20 for a layered Fe/Si composite of stoichiometry 1/2 iron/silicon showing sample evolution with annealing. Curves A through C correspond to points A through C in Figure 8. The upper curve is data synthesized from the JCPDS diffraction files for a sample of crystalline FeSi2. The curves are offset for clarity.

The responsibility for the maintenance of the Powder Data File lies with the International Centre for Diffraction Data (JCPDS), which is a nonprofit organization located in Swarthmore, Pennsylvania. This group is made up of a staff of permanent officers along with a number of academic and industrial scientists who are active in the field of X-ray powder diffi actometry. The Powder Data File is a unique assembly of good-quality single-phase patterns and is used by thousands of chemists, geologists, and materials scientists. The automation of the search/match process promises to make the use of the file even more widespread, since this should do much to relieve much of the tedium associated with manual search/matching. 

International Center for Diffraction Data, 1991, JCPDS Inorganic Files, Swarthmore, USA. 

Powder Diffraction File, Pub. SMA-29, JCPDS, International Centre for Diffraction Data, Swarthmore, Pa., 1979. 

Table 2.1 shows the crystal structure data of the phases existing in the Mg-H system. Pnre Mg has a hexagonal crystal structure and its hydride has a tetragonal lattice nnit cell (rutile type). The low-pressure MgH is commonly designated as P-MgH in order to differentiate it from its high-pressure polymorph, which will be discussed later. Figure 2.2 shows the crystal structure of p-MgH where the positions of Mg and H atoms are clearly discerned. Precise measurements of the lattice parameters of p-MgH by synchrotron X-ray diffraction yielded a = 0.45180(6) mn and c = 0.30211(4) nm [2]. The powder diffraction file JCPDS 12-0697 lists a = 0.4517 nm and c = 0.30205 nm. The density of MgH is 1.45 g/cm [3]. 

McClune, W.F., editor-in-chief, Powder Diffraction File, JCPDS-International Centre for Diffraction Data, Swarth-more, PA. 

The Mineral Powder Diffraction File. Joint Committee for Powder Diffraction Standards (JCPDS), International Center for Diffraction Data, Swarthmore, Pennsylvania (updated continuously). 

The simplest application of powder diffraction is to identify a crystalline phase. One merely runs the powder pattern of the solid and records either 29 values or rf-spacings or both. This information is given by the program and can be printed directly on the pattern. Then one may consult a database such as the JCPDS file. These initials refer to the JCPDS. As a result of the complexity of keeping pace with the ever growing fist of known phases, the operation grew and was renamed the International Centre for Diffraction Data (ICDD), headquartered in Newton Square, Pennsylvania. 

FIGURE 16.5. Data for two salts from the Powder Diffraction File. The crystal system, unit-cel] dimensions, space group and bibliographic references are given together with experimental details. Listed on the tight ate dhki, I hkl) and hkl for the most intense Bragg reflections. Courtesy, JCPDS — International Centre for Diffraction Data (ICDD), publishers of the Powder Diffraction File. 

Fig. 14-1 Standard 3 x 5 in. JCPDS diffraction data card (card 628 from Set 5) for sodium chloride. Appearing on the card are 1 (file number), 2 (three strongest lines), 3 (lowest-angle line), 4 (chemical formula and name of substance), 5 (data on diffraction method used), 6 (crystallographic data), 7 (optical and other data), 8 (data on specimen), and 9 (diffraction pattern). Intensities are expressed as percentages of Ii, the intensity of the strongest line on the pattern. Most cards have a symbol in the upper right comer indicating the quality of the data (high quality), i (lines indexed, intensities fairly reliable), c (calculated pattern), and o (low reliability). (Courtesy of Joint Conunittee on Powder Diffraction Standards.)...

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