The absorption of X-rays in a heterogeneous material depends on the linear absorption coefficients and volume fractions of the components, and on die geometrical peculiarities of their distribution. The latter is called the microabsorption effect, it can be separated into a bulk and a surface contribution. Within the framework of a well-defined stochastic structure model, the bulk contribution to the microabsorption is calculated for arbitrary random multiphase systems in terms of dependence on volume fractions and mean chord lengths of particles. Expressions are derived which are suitable for eliminating the experimental errors of scattering intensities caused by the bulk contribution of microabsorption.

If only one wavelengtii of radiation is used, the mean chord lengths of the phases of the sample must be determined by other experimental techniques. A method is proposed to overcome this difficulty by using two or more wavelengths of radiation; this correction procedure works without the knowledge of the particle sizes of the phases.

Quantitative phase analysis of n-phase mixtures can be performed if at least n samples composed of no more than n identical phases are available. The fact that there is no need for pure phases (analytical standards) constitutes the main advantage of the method presented here. However, substitution for the pure phases by an unknown mixture of these phases decreases the diversity of the sample set and also the precision of the analysis. The crucial step in a standardless method is the creation of an initial sample set. A simple test is developed to estimate the suitability of the sample set for analysis and to evaluate the analysis error. Application of this test to 13 four-phase mixtures has confirmed its high quality.

This is a second and considerably expanded edition of the RIR table. We are pleased that considerable interest is now being generated in the RIR table; several contributors have provided measured data for this second edition. We have also added many entries of common minerals and simple compounds from the JCPDS data base and will continue to add more from this source with each succeeding table published. In this regard where we receive requests for a particular class of RIR's (alloys, or rare earth oxides, for examples) we can give higher priority to extracting these values from the JCPDS data base.

The reader should refer to the text explanation of the first published table in Vol. 3, No. 4 of this journal. In the first text two important errors are noted here; Equation (3) should have read RIRcorr = RIRobs/Wj; and the second sample preparation category of section 4 Specific Parameters should read “(w) Methods including well mounts with side or back loading or similar process”.

A commercially available photoconductor material, p-diethylaminobenzaldehyde diphenylamine hydrazone, C23H25N3, has been purified and recrystallized from an absolute alcohol solution. The triclinic compound has been characterized by X-ray powder diffraction. Experimental 2θ values corrected for systematic errors, relative peak intensities, values of d, and the Miller indices of 74 observed reflections with 2θ up to 30.5° are reported. The powder diffraction data have been evaluated, and figures of merit are reported. Unit-cell parameters least-squares refined from the 74 observed reflections of the triclinic compound are in good agreement with those obtained from the single-crystal structure analysis.

Quartz in dolostone can be determined quantitatively down to 0.03 weight percent using a standard preparation procedure for the sample and absolute integrated intensity measurements. Measurement reproducibilities of 3.2% were obtained. Calibration curves determined by spiking low-quartz dolostone allowed concentrations of 2.0 weight percent or lower to be established. Higher concentrations of quartz in some related soil samples were determined by comparing the absolute integrated intensity with that obtained from a pure quartz sample prepared in the same manner.

Crystal data are given for synthetic mixed bariumstrontium sulfates, and a powder pattern for (Ba0.50Sr0.50)SO4 is presented. Taken with previously published data for the end-member sulfates, we verify the nonlinear behavior of the unit-cell edges with composition, and present tables of interpolated data from which d-spacings for intermediate compositions can be calculated. The use of these data for analysis of complex natural samples by use of the 121 peak is described.

Palladium tetrammine dichromate, [Pd(NH3)4]Cr2O7, was obtained by precipitation from [Pd(NH3)4]Cl2·H2O and (NH4)2Cr2O7. The X-ray diffraction pattern of this compound corresponds to a new phase, which was indexed in the triclinic system, but on a cell that should be considered as preliminary. From the chemical analysis and the X-ray absorption experiments at both K-edges of Pd and Cr, we conclude that the surrounding of these atoms is kept during formation.

New X-ray powder data for CaWO4 (synthetic scheelite) are presented and compared with the current PDF patterns and with a calculated pattern.

Crystallographic and X-ray powder diffraction data were derived from a sample of (Na0.5Bi0.5)TiO3 synthesized by standard ceramic techniques. The powder data were indexed on a monoclinic cell having the space group P2 or Pm, which differed from a previously reported rhombohedral cell.

Nickel Cimetidine Chloride, Ni(C10H16SN6)2Cl2·2H2O has been investigated by means of X-ray powder diffraction. Unit cell dimensions were determined by indexing programs, from diffractometer data obtained with copper radiation. A primitive monoclinic cell was found: a = 11.836(3)Å, b = 13.322(5)Å, c = 10.487(2)Å, β = 113.08 (2)°, Z = 2, Dx = 1.462 g/cm3, M.W. = 670.32. These data are consistent with values reported in the literature for other cimetidine complexes.

New powder and crystallographic data for gorceixite, a mineral of the crandallite subgroup of the alunite group, are reported and compared with current Powder Data File (PDF) patterns and with calculated patterns. Both d-spacings and intensities have been evaluated, and the results indicate a significant improvement over existing patterns. Indexing of the reflections is given for the true monoclinic symmetry, Cm (8), the pseudorhombohedral symmetry, (166) (to compare with structurally analogous minerals), and the pseudocubic symmetry, Fm3m (225). Because of the strong pseudosymmetry, the overall figure of merit is lower than would be the case for indexing in one of the pseudospace groups.

X-ray powder diffraction data for the compound 2-nitro-l-phenyl-prop-l-ene, C9H9NO2 are reported. The crystals are orthorhombic and the space group is Pbca[61], with a = 7.576(2), b = 19.452(5), c = 11.269(4)Å, Z = 8 Dx = 1.305, Dm = 1.300(2) g/cm3.

Two ammonium copper molybdates having the stoichiometric compositions (NH4)2Cu(MoO4)2(NH3)2 and (NH4)2Cu(MoO4)2 have been synthesized from aqueous solutions. The compounds crystallize in the triclinic system with space group . Crystal data and indexed X-ray powder diffraction data are reported for both phases.