Standard x-ray diffraction patterns are presented for 86 substances. Fiftyeight of these patterns represent experimental data and 28 are calculated. The experimental x-ray powder diffraction patterns were obtained with an x-ray diffractometer. All d-values were assigned Miller indices determined by comparison with computed interplanar spacings consistent with space group extinctions. The densities and lattice constants were calculated and the refractive indices were measured whenever possible. The calculated x-ray powder diffraction patterns were computed from published crystal structure data. Both peak height and integrated intensities are reported for the calculated patterns. Key words: Crystal structure; integrated intensities; lattice constants; peak intensities; powder patterns; reference intensities; standard; x-ray diffraction. INTRODUCTION 1 The Powder Diffraction File is a continuing compilation of diffraction patterns gathered from many sources. Produced and published by the JCPDS--International Centre for Diffraction Data the File is used for identification of crystalline materials by matching d-spacings and diffraction intensity measurements. Under the partial sponsorship of the JCPDS, the program at the National Bureau of Standards contributes new data to this File. Our work also aids in the evaluation and revision of published x-ray data and in the development of diffraction techniques. This report presents information for 86 compounds (58 experimental and 28 calculated patterns), and is the twentysixth of the series of "Standard X-ray Diffraction Powder Patterns "12 EXPERIMENTAL POWDER PATTERNS CAS registry number. The Chemical Abstracts Service Registry Number is included, when available, to help identify the sample. This number forms the basis for computer aided searching of Chemical Abstracts. JCPDS--International Centre for Diffraction Data, 1601 Park Lane, Swarthmore, PA. 19081. This Pennsylvania non-profit corporation functions in cooperation with the American Ceramic Society, the American Crystallographic Association, the American Society for Testing and Materials, The Clay Minerals Society, The Institute of Physics, the Mineralogical Association of Canada, the Mineralogical Society of America, The Mineralogical Society of Great Britain and Ireland, the National Association of Corrosion Engineers, and the Société Française de Minéralogie et de Cristallographie. 2See previous page for other published volumes. Sample. The samples used to make NBS patterns were obtained from a variety of sources or were prepared in small quantities in our laboratory. Appropriate annealing or recrystallization of the samples improved the quality of most of the patterns. A check of phase purity was provided by indexing the x-ray pattern. Optical data. When reported, optical measurements were made by grain immersion methods, in white light, using oils standardized in sodium light, in the refractive index range 1.49 to 2.1 [Hartshorne and Stuart, 1970]. The names of the sample colors were selected from the ISCC-NBS Centroid Color Charts [1965]. Interplanar spacings. For spacing determinations, a shallow holder was packed with a sample mixed with an internal standard. Choice of the standard was determined by the need for low angle and unobstructed reflections. The amount of standard was estimated so that the intensity of its strongest peak would be about equal to the intensity of the strongest peak of the sample. To avoid errors associated with aberrations at the very top of the peaks, the readings of 20 were taken at positions about 20% of the way down from the top, and in the center of the peak width. The Ka2 peaks were occasionally read to assist in establishing a Kaj peak position, but Ka2 peaks were not reported. At low angles, Kay and Ka2 peaks were unresolved for both the sample and the internal standard. The internal standard corrections were established from the theoretical values for Kay and were applied to the unresolved low angle peaks, as well as to the resolved Ka, peaks in the higher angle regions. If the internal standard correction varied along the length of the pattern, linear interpolations were used. The new internal standard Si powder is available as Standard Reference Material 640 [1974]. The lattice constant for the Si was refined from multiple powder data measurements made with tungsten as an internal standard [Swanson et al., 1966]. Cell parameter data were also collected for single crystal from the boules ground to prepare the powder. The lattice parameters from the two methods agreed within 3 parts in 105 [Hubbard et al. 1975]. D-spacing results using SRM 640 will be in agreement with patterns recorded in this series of monographs since 1966. All of our spacing measurements were recorded at 251 °C on a diffractometer equipped with a focusing graphite or lithium fluoride crystal monochromator located between the sample and the scintillation counter. Pulse height discrimination was used as well. All measurements were performed using copper radiation: A (CuKa1, peak)=1.540598Ă [Deslattes and Henins, 1973]. Structure, lattice constants. The space groups were listed with short Hermann-Mauguin symbols as well as the space group numbers given in the International Tables for X-ray Crystallography, Vol. I (1952]. Orthorhombic cell dimensions were arranged according to the Dana convention b>a>c [Palache et al., 1944]. Monoclinic and triclinic lattice constants were transformed if necessary in order to follow the convention of Crystal Data [1973]. A computer program [Evans et al., 1963] assigned hk's and refined the lattice constants. Cell refinement was based only upon 20obs values which could be indexed without ambiguity. The program minimized the value (obs-calc)2. The estimated standard deviations (e.s.d.'s) of the reciprocal cell parameters were determined from the inverse matrix of the normal equations. The program calculated the e.s.d.'s of the direct cell constants by the method of propagation of errors. Since 1973, the e.s.d.'s derived by the computer program have been increased by 50% in order to reflect more truly the uncertainty in the lattice constants. similar increase should also be applied to all lattice constants in earlier publications of this series. The e.s.d.'s in the least significant figures are given in parentheses following the lattice constants. A In indexing cubic patterns, multiple hkl's were not utilized in the refinement or reported. Instead, the single appropriate index having the largest h was listed. The number of significant figures reported for d-values varied with the symmetry and crystallinity of each sample. Densities. These were calculated from the specified lattice constants, the Avogadro number 6.0220943 x 1023 [Deslattes et al., 1974] and atomic weights published by the International Union of Pure and Applied Chemistry [1972]. Figure of merit. Several figures of merit ratings are available for assessing indexed powder data. M20 [de Wolff, 1968] is a criterion for the reliability of the unit cell and indexing. A value of M20 10 will guarantee the essential correctness of the indexing provided there are not more than 2 spurious lines (X202) [de Wolff, 1968]. All patterns reported in this publication have M20 between 20 and 233, and X20 O unless noted otherwise. M20 was specified for any pattern indexed with a cell derived only through computer indexing from powder data, without further confirmation. = The accuracy and completeness of measured interplanar spacings is conveniently reported as FN [Smith and Snyder, 1979]. The format used in this publication was FN = overall value (20, Nposs), where N, the number of observed reflections was chosen as 30 or the maximum number of lines of the pattern, if the entire pattern had fewer than 30 lines. The "overall value" was the figure of merit, FN, as defined by Smith and Snyder [1979], and A20 was the average absolute magnitude of discrepancy between observed and calculated 20 values for the N lines. Nposs was the number of unique and resolvable diffraction lines allowed in the space group, up to the Nth observed and indexed line. In this publication, the value of FN ranged from 31 to 118, with an average value of 61 for the 58 patterns from experimental data. Intensity measurements. It was found that samples which gave satisfactory intensity patterns usually had an average particle size smaller than 10 μm, as recommended by Alexander et al. [1948]. In order to avoid the orientation effects which occur when powdered samples are packed or pressed, a sample holder was made that had in its top face a rectangular cavity which extended to one end of the holder. To prepare the sample, a glass slide was clamped over the top face to form a temporary cavity wall (see Figure 1), and the powdered sample was allowed to drift into the end opening while the holder was held in a vertical position. With the sample holder returned to a horizontal position, the glass slide was carefully removed so that the sample could be exposed to the x-ray beam (see Figure 2). If the sample powder did not flow readily, or was prone to orient excessively, approximately 50 volume percent of finely ground silica-gel was added as a diluent. The intensities of the diffraction lines were measured as peak heights above background and were expressed in percentages of the strongest line. Any intensity larger than 20 was rounded to the nearer multiple of 5. At least 3 patterns for intensity measurements were prepared for each sample to check reproducibility. Reference Intensity Ratio, I/I, corundum. The reference intensity ratio, I/Ic, has been defined as the direct ratio of the intensity of the strongest reflection of a sample, to the intensity of the reflection 113 (hexagonal) of corundum (a-A1203) [Visser and de Wolff, 1964]. In this publication, the ratios I/Ic were tabulated for copper Ka radiation, for a 1:1 mixture by weight of the sample and corundum. Occasionally I/I was not determined because it was not feasible. Format of tables. The printing of the data has been computerized. Superimposed reflections were treated in one of two ways. If a d-spacing had only two possible indices, an M was added to the dspacing which was repeated on the next line, but with the second index. However, if there were more than two possible indices, a sign was used in like manner. In both cases, the composite intensity was printed only once and aligned with the first reflection. The symbol "1L" in the intensity column was used to indicate "less than 1." CALCULATED POWDER PATTERNS Since some substances of interest are not readily available for experimental work, powder patterns were calculated from published crystal structure data. The FORTRAN program used for the computations was developed by Clark et al. [1973] and modified at NBS. Lattice parameters. Before the computations of the patterns, any necessary changes were made consistent with the revised value of λ(CuKa])= 1.540598A [Deslattes and Henins, 1973]. Both the altered and the original published values are given. A lattice constant arrangement which follows the convention of Crystal Data has been referred to as the "CD cell." In several of the calculated patterns, the literature lattice constants, the atom positions, and hence the final patterns were not given in the CD arrangement. For cross-reference purposes, the CD cell was calculated separately and included in the text. The primes denoted the values for the largest integrated intensity. In earlier Monographs (1969-1975), a different scale factor, kNBS, was reported which is related to y: B = 4 Structural information. The atom positions used in these calculated patterns varied somewhat in the degree of reliability. In our text, when the expression "the structure was determined by..." was used, the atomic parameters in the reference cited had been calculated from refinement of single crystal data. Otherwise, the atomic positions had been derived by analogy with similar compounds whose structure was known. In cases where isostructural relationships were used, the atoms were in fixed special positions or the ionic radii were closely related to the corresponding radii of the atoms in the known structure. From y, the theoretical value of the Reference was calculated: Intensity Ratio, I/I¿' I/Ic and y are each based on the single strongest reflection, not on the overlapping sum of superimposed reflections. Peak heights. The purpose of calculating peak height intensity was to provide a tabulated pattern similar to what might be obtained from experimental diffractometer measurements. For each predicted reflection, Cauchy profiles centered at both the a1 and the a2 peak positions were calculated and summed, forming a simulated powder pattern. The full width at half-maximum (FWHM) as a function of 20. [The values of the FWHM vs 20 are given in Table 2.]. The resultant simulated powder pattern was then analyzed for peaks. In the regions of the predicted reflections several reflections could have identical or similar 20 angles and produce only one composite peak in the simulated pattern. The 20 angle of the composite peak was assigned the hkl of the reflection having the greatest contribution to the peak height intensity. If any other peak contributed more than 10% of the intensity toward the composite peak height intensity, a plus sign(+) was appended to the hkl. In this publication the Ångström unit (1Å= 100pm) was selected for presentation of the dspacings and lattice parameters to maintain consistency with (a) the earlier publications of Standard X-ray Diffraction Powder Patterns (Circular 539 volumes 1-10 and Monograph 25 sections 1-15), (b) the publications of the International Union of Crystallography: Acta Crystallographica and the Journal of Applied Crystallography, and (c) the continuing publication of cards and search manuals of the Powder Diffraction File (now consisting of nearly 30,000 entries). The PDF search manuals are based on the d-spacings in A of the three strongest lines. Consistent with the choice of the A unit for length, the volume of the unit cell is expressed in Å3 (=1 x 10-30 m3). Other reported parameters and their units are density in g/cm3 (1 gm/cm3 10-3 kg/m3) and the linear absorption coefficient in cm-1. ACKNOWLEDGMENTS = We would like to thank Mary Owen of the JCPDS Associateship for her assistance, particularly for key-punching the data and helping with the proofreading of this manuscript. Appreciation is also expressed to the Text Editing Facilities of the National Measurement Laboratory of NBS for typing the manuscript. Alexander, L., Klug, H. P. and Kummer, E. (1948). Clark, C. M., Smith, D. K., and Johnson, G. G., Jr. Crystal Data (1973). (3rd. Ed. Published jointly Deslattes, R. D., Henins, A., Bowman, H. A., Schoonover, R. M., Carroll, C. L., Barnes, I. L., Machlan, L. A., Moore, L. J., and Shields, W. R. (1974). Phys. Rev. Lett. 33, 463. Evans, H. T., Jr., Appleman, D. E. and Handwerker, D. S. (1963), Report #PB 216188, U.S. Dept. of Commerce, National Technical Information Center 5285 Port Royal Rd., Springfield, VA 22151, $3.50. Hartshorne, N. H. and Stuart, A. (1970). and the Polarizing Microscope and Co., London, 4th Ed.) Crystals (Edward Arnold Hubbard, C. R., Evans, E. H., and Smith, D. K., Hubbard, C. R., Swanson, H. E., and Mauer, F. A. (1952). (The Kynoch Press, Birmingham, Eng.), Ibid. III (1962) pp. 202, 210, 213, 214. International Union of Pure and Applied Chemistry (1972). Pure Appl. Chem. 30, Nos. 3-4, 639. ISCC-NBS Centroid Color Charts, SRM 2106, or Color Kit, SRM 2107 which contains both SRM 2106 and Color, an NBS Special Publication #SP 440. These can be obtained from the National Bureau of Standards, Office of Standard Reference Materials, Washington, D.C. 20234. Current prices will be quoted on request. Palache, C., Berman, H. and Frondel, C. (1944). Visser, J. W. and de Wolff, P. M. (1964). "Abso- Wolff, P. M. de (1968). J. Appl. Crystallogr. 1, 108. |