The mathematical relationships are developed which are pertinent to the quantitative analysis of powder mixtures for the case of diffraction from the surface of a flat powder specimen. These formulas relate the diffracted intensity to the absorptive properties of the sample. Three important cases are treated: (1) Mixture of n components; absorbing powder of the unknown equal to that of the matrix; concentration proportional to intensity. Direct analysis is permitted. (2) Binary mixture; absorbing powder of the unknown not equal to that of the diluent; concentration not proportional to intensity. Direct analysis is possible by means of calibration curves prepared from synthetic mixtures. (3) Mixture of n components; absorbing power of the unknown not equal to that of the matrix; general case. Analysis is accomplished by the addition of an internal standard. Concentration is proportional to the ratio of the intensity of a selected reflection from the unknown to the intensity of a reflection from the internal standard.

A quantitative phase analysis often requires advanced numerical studies to determine the appropriate intensity values. In this paper the method of fitting analytical functions to the experimental profile is applied to X-ray powder diffraction patterns obtained with FeK radiation. In the present work, the authors examine some problems connected with numerical studies, especially the function describing the experimental profile. The usefulness of the α2 elimination procedure and the angular dependence FWHM are also examined.

The intensity round-robin is one of a series of round-robins sponsored by the International Centre for Diffraction Data. The purpose of these round-robins is to attempt to quantify problems encountered in the acquisition, analysis and interpretation of powder diffraction data. Previous International Centre sponsored round-robins have addressed topics including: manual and automated search match methods; sample preparation methods; d-spacing accuracy; cell parameter refinement and peak profile calibration.

The primary focus of the intensity round-robin was to study measured intensities obtained from modern computer controlled powder diffractometers. However, the tests were designed in such a way as to also yield information on the performance of data treatment software packages. To this end, participants were asked to submit both raw and treated data, thus allowing evaluation of, for example, the efficiency of peak hunting algorithms in finding peaks.

Crystal data and a representative X-ray powder diffraction pattern are reported for a series of isomorphous compounds, LnKFe(CN)6.4H2O where Ln = La, Ce, Pr and Nd. They crystallize in the hexagonal space group P63/m (176) with Z = 2. A plot of the unit cell volume (V) versus the cube of the Ln ionic radius (r3) yields linearity with a correlation coeficient of 0.9998.

Based on analysis of its powder diffraction pattern, tetracycline hydrochloride is orthorhombic; the space group is probably P212121(19) or P21212(18). Indexed powder data and refined cell parameters are presented.

Fifteen reference patterns of oxide ceramics are reported. Included in the fifteen reference patterns are data for nine high critical temperature superconducting oxide and related phases Ba2Cu3ErO7, Ba3.2Cu1.7Er0.8O6.1·xCO2, Ba2Cu3HoO7, Ba2Cu3(Pr0.5Y0.5)O7, Ba3Dy4O9, Ba3Yb4O9, (Ba0.6Sr0.4)2Cu3YO7, (Ba0.8Sr0.2)2Cu3YO7, and CuNd2O4. The general methods of producing diese X-ray powder diffraction reference patterns were described previously in this journal (Vol. 1, No. 1, pg. 40 (1986)). The symbols used in diis article are defined in the PDF cards.