The Powder Diffraction File (PDF) is a collection of single phase X-ray powder patterns, maintained and distributed by the JCPDS-International Centre for Diffraction Data. Over the past 10 years there has been increasing use of the PDF in computer readable form, but the limited amount of disk space available on most commercial powder diffractometer systems has limited use to a small subset of the total PDF. The recent availability of low-cost Compact Disk Read Only Memory (CD-ROM) systems offers an attractive alternative to conventional disk media. This paper describes a low-cost Personal Computer/CD-ROM system, “PC-PDF”, having a total available storage of 550 Mbytes. While seek times are relatively slow – typically, 0.5 seconds are required to traverse the complete PDF – by use of optimum packing and access algorithms, search strategies based on PDF numbers, chemistry, strongest d-spacing, etc., operate at a speed causing no great inconvenience to the user.

Calculations of crystal size distributions in oriented clays (montmorillonite and kaolinite) are carried out utilizing X-ray diffraction data together with a method based on information theory. Two different procedures for dealing with the available data are compared. One of them involves some points of the corresponding spectrum, the other correlates the data by means of their moments.

Magnesium-chlorophoenicite may be differentiated from the Mn-analogue chlorophoenicite, because for magnesium-chlorophoenicite at 7Å, whereas for chlorophoenicite.

In a review of the literature for the Mineral Powder Diffraction File by Bayliss et al. (1980), powder X-ray diffraction data could not be found of the mineral species magnesium-chlorophoenicite, (Mg,Mn)3Zn2(AsO4)(OH,O)6. Dunn (1981) states that the powder X-ray diffraction data of magnesium-chlorophoenicite is essentially identical to that of chlorophoenicite (Mn analogue) and confirms that the minerals are isostructural.

With the crystal structure parameters determined by Moore (1968) for a Harvard University specimen from New Jersey of chlorophoenicite, a powder X-ray diffraction pattern was calculated with the programme of Langhof, Physikalische Chemie Institute, Darmstadt. The calculated pattern was used to correct and complete the indexing of the powder X-ray diffraction data of chlorophoenicite specimen ROM M15667 from Franklin, Sussex County, New Jersey, U.S.A. by the Royal Ontario Museum (PDF 25-1159). With the correctly indexed data of ROM M15667, the unitcell parameters were refined by least-squares analysis and are listed in Table 1.

The most magnesium-rich magnesium-chlorophoenicite found in the literature is a description of Harvard University specimen 92803 from Franklin, Sussex County, New Jersey, U.S.A. by Dunn (1981), where Mg is slightly greater than Mn. A 114.6 mm Debye-Schemer film taken of HU92803 with Cu radiation and a Ni filter (CuKα = 1.5418Å) was obtained from Dr. P. Dunn and measured visually. The unit-cell parameters, which were refined by least-squares analysis starting from the unit-cell parameters of PDF 25-1159 in space group C2/m(#12), are listed in Table 1, and give F28 = 4.1(0.050,136) by the method of Smith & Snyder (1979).

The hkl, dcalulated, dobserved and relative intensities (I/I1) of HU92803 are presented in Table 2. With the atomic positions and temperature factors of chlorophoenicite determined by Moore (1968), the Mn atomic positions occupied by 50% Mg and 50% Mn, and the unit-cell parameters of HU92803, a powder X-ray diffraction pattern was calculated and Icalculated is recorded in Table 2. A third powder X-ray diffraction pattern was calculated with the Mn atomic positions fully occupied by Mg. Because the atomic scattering factor of Mn is more than twice greater than Mg, chlorophoenicite may be differentiated from magnesium-chlorophoenicite based upon the calculated intensities of the first three reflections given in Table 3.

Although the a, c and β unit-cell parameters of chlorphoenicite are similar to those of magnesium-chlorphoenicite, the b unit-cell parameter of chlorophoenicite is significantly greater than that of magnesium-chlorophoenicite (Table 1). The b unit-cell parameter represents the 0–0 distance of the Mn octahedra (Moore, 1968). Since the size of Mn is greater than that of Mg, chlorophoenicite may be differentiated from magnesium-chlorophoenicite based upon the b unit-cell parameter given in Table 1.

American Museum of Natural History (New York, N.Y., U.S.A.) specimen 28942 from Sterling Hill, Ogdensburg, New Jersey is composed of willemite, haidingerite and magnesian chlorophoenicite. A spectrographic analysis of the magnesian chlorophoenicite shows As, Mg, Mn and Zn. Powder X-ray diffraction data (PDF 34-190) of the magnesian chlorophoenicite was collected by diffractometer with Cu radiation and a graphite 0002 monochromator (Kα1 = 1.5405) at a scanning speed of 0.125° 2θ per minute. The unit-cell parameters, which were refined by leastsquares analysis starting from the unit-cell parameters of PDF 25-1159, are given in Table 1. Specimen AM 28942 is called chlorophoenicite, because of its large b unit-cell parameter (Table 1), and the I/I1 of 25 for reflection 001 and of 50 for reflection 201 compared to the Icalculated in Table 3.

A Siemens D500 powder diffractometer has been modified to accommodate data collection and storage by an IBM microcomputer. The interface mechanism, described in detail, is simple, versatile and relatively low cost. The system performance is evaluated and further enhancements suggested.

50-50 atomic percent lead telluride (Altaite), grown by the vapor transport method, was examined with a well aligned Rigaku horizontal beam diffractometer. PbTe is cubic (precise lattice parameter ao = 6.4591(5)Å) with an space group and a calculated density of 8.253 g/cm3. Fully indexed powder diffraction data are presented.

Crystalline structures of one single- and two multi-layer magnetic CoCrTa films were characterized by X-ray powder diffraction technique. Structural parameters such as crystalline phase, preferred orientation, crystallite size and microstrain (which control the magnetic properties) have been determined. Polycrystalline diffractions from lattice planes parallel and perpendicular to the surface of a film were obtained with the specimen in reflection and in transmission, respectively. Phase identification of the ternary alloy (Co85Cr15)90Ta10 magnetic layers of the specimens indicated a disordered solid solution of Cr and Ta in Co, and the alloy has a hexagonal close-packed (h.c.p.) (A3) structure. Line broadening analysis showed crystallite size anisotropy and columnar CoCrTa grains. The crystal growth was disrupted by the nonmagnetic “amorphous” spacing layers in the multi-layer specimens. The disruption increased with the decreasing magnetic layer thickness. Compared to those of the single-layer film, a lesser (00l) basal plane preferred orientation with a larger perpendicular c-axis dispersion, smaller crystallite sizes and higher microstrains at L≥50Å were obtained in the multi-layer specimen consisting of eight 500Å thick magnetic layers. The magnetic particles were found to be poorly crystallized in the multi-layer specimen where the thicknesses of the 33 magnetic layers were limited to 150Å each.

Accurate, digitized, spectral distribution data are given for CuKα radiation, comprising the profiles of CuKα1, CuKα2 and CuKα3,4. Three consistent analytical procedures are detailed for locating the peak of an X-ray emission line and are found to be superior to the conventional graphical centerline method.

External standard and internal standard calibrations are important procedures for achieving high accuracy in X-ray powder diffraction studies. The theoretical basis as well as procedures for obtaining calibration curves are given. Methods and examples of selecting Standard Reference Materials (SRMs) which are produced and issued by the National Bureau of Standards (NBS), and procedures of sample preparation with these standards are also described. Three examples are presented to indicate the value of using SRMs.

Possibilities and restrictions of least-square methods for mica cell refinement are briefly described. If diffractometric raw data are precise and accurate, and if geometrical errors are properly corrected, a cell refinement (determination of ao, bo, cO, β) can be carried out rapidly, but the reliability of obtained data has to be evaluated carefully.

Potassium calcium phosphate, KCa PO4.H2O, has been investigated by means of X-ray powder diffraction. Unit cell dimensions were determined from diffractometer data obtained with strictly monochromatized Cu Kα1 radiation, by indexing programs. A C-centered monoclinic cell was found: a =7.5834(9) Å, b = 8.1568(11) Å, c = 7.6541(8) Å, β= 102.975 (9)°.

Indexed powder patterns are reported for three homogeneous metastable ZrO2-CeO2 solid solution members with high-zirconia [(ZrO2)x mole fraction, x>.84 –.80] and lowzirconia (.60>x>.40) compositions. The primitive cell dimensions are: a = 3.6377(7) Å and c = 5.2394(11) Å at x = 0.84, and a = 3.7205(5) Å and c = 5.3039(7) Å at x = 0.5. Samples with intermediate compositions are heterogeneous. Also reported are powder data for the cubic (fluorite-structure) solution from a sample with x = 0.40 and a slightly different thermal history.

Fifteen reference patterns of boride, silicide, selenide, telluride and oxide ceramics are reported. Included in the 15 reference patterns are data for three oxide phases which are related to high critical temperature (Tc) superconducting materials: BaCuO2, BaCuSm2O5 and BaCuYb2O5. Four other patterns are included which represent phases previously not contained in the PDF. The remaining six are major corrections of data already included in the file. Reference data for phases Ba2CuY3O6.8 and Ba2Y3CuO6 appeared in the special July superconductor issue of the Advanced Ceramic Materials, 1987. The general methods of producing these X-ray powder diffraction reference patterns are described in this journal, Vol. 1(1), 40 (1986).

Samples were mixed with one or two internal standards: silicon (SRM640a), silver, tungsten, or fluorophlogopite (SRM675). Expected 2θ values for these internal standards are specified in the methods described (ibid.). Data were measured with a computer controlled diffractometer. The POWDER-PATTERN system of computer programs was used to locate peak positions, to calibrate the patterns, and to perform variable indexing and least-squares cell refinement. A check on the overall internal consistency of the data was also provided by a computer program.