A simple, practical search/match program, RIFRAN 85, has been written and implemented for the EMG 666B programmable calculator. The computer programs are written in EMG Assembler, which is identical to the assembler language for the Hewlett-Packard 9821 calculator. The EMG 666B is made in Hungary and has 8 kbytes of operational memory. The programs interactively provide qualitative phase analysis of X-ray powder diffraction patterns using standard files collected from published data and stored on a compact magnetic tape cassette. Each standard pattern can comprise up to 35 two-theta — intensity pairs. The identification procedure is based on the comparison of the diffraction data of the standard and of the unknown within limits imposed by user-established match and chemical criteria. This paper describes the algorithm used and the performance of the RIFRAN 85 identification system. The system's operation is illustrated using an example of phase analysis of a mineral sample.

Crystals of sodium copper oxalate dihydrate [Na2Cu (C2O4)2.2H2,O] were obtained by the gel method, from solutions of oxalic acid and copper chloride. The crystals form blue needles with idiomorphic faces of brilliant luster, permitting goniometric measurements and the determination of the morphology with the aid of crystallographic parameters. Optically the crystals are biaxial negative, 2V = 38°, with a weak dispersion r<v. The orientation of the indicatrix was determined using a universal stage.

Crystals of sodium copper oxalate dihydrate, Na2Cu (C2O4)2.2H2O, were apparently first obtained in 1929 by Riley. Gleizes et al. (1980) undertook a preliminary crystallographic study of crystals obtained by a different technique from Riley's. In the first case, a solution of 33.5 g/L of sodium oxalate was heated and then poured gradually into a nearly saturated solution of copper sulfate until slight turbidity appeared. The turbidity was eliminated and the solution clarified by the addition of a little more sodium oxalate solution. In this way Riley obtained a dark blue solution which after filtration yielded extremely fine sky-blue needle-like crystals, rarely more than 8mm long. In the method of Gleizes et al. (1980), copper oxalate was dissolved in an aqueous solution of sodium oxalate; those authors observed complete dissolution when the molar ratio of sodium oxalate to copper oxalate was near 2. By evaporating the solution, they obtained long, prismatic crystals whose crystallographic constants they determined.

In order to obtain crystals large enough for further crystallographic study, we set out to produce crystals of sodium copper oxalate by the gel method (Triché, 1984). We found that slow crystallization did encourage the formation of large crystals.

Indexed X-ray diffraction powder data for three homologous amphiphiles, sodium octyl sulfate (SOS), CH3[CH2]7 OSO3Na, sodium decyl sulfate, CH3[CH2]9OSO3Na (SDS), and sodium dodecyl sulfate CH3[CH2]11OSO3Na (SLS), are reported. Probable space groups for the three compounds are monoclinic P2[3], Pm[6], or P2/m[10]. Refined cell parameters were determined from powder data obtained with a Guinier Camera. Powder data are compared to existing patterns, PDF 4-10 (SOS) and 4-6 (SLS).

X-ray powder diffraction of Nitrofurantoin C8H6N4O5 reveals that the compound crystallizes in a monoclinic unit cell with the powder data unit cell parameters of a = 7.852(2), b= 6.497(1), c = 18.927(5) Å, β=93.15(2)°, V=964.1(2) Å3. The unit cell dimensions determined by single crystal agree very well with those of powder diffraction analysis. A comparison with the Powder Diffraction File (PDF) 34-1603 indicates that the present data provide a more precise match to the unit cell, include additional weak reflections, along with the indexing of the powder pattern.

The accuracy of the unit-cell parameters refined by using the whole-powder-pattern decomposition method is discussed. Powders of W, ZnO, TiO2, BaTiO3 Mg2SiO4, Al2SiO5 (+α-SiO2), and monoclinic ZrO2 were used as test samples. Two internal standard reference materials of Si and CeO2 and two types of powder diffractometers were used for data collections. The systematic peak-shift was corrected by determining the unit-cell parameters and the error function simultaneously during the whole-pattern-fitting. The estimated standard deviations for sample means ranged from <10 ppm (10−6) in cubic symmetry to 20∼50 ppm in monoclinic symmetry. These analyses could be carried out almost automatically in a computation time of less than l min for each sample on a workstation. The use of symmetric experimental profiles, obtained by the suppression of axial divergence, is very effective and of essential importance for improving the accuracy of unit-cell parameters.

A technique is presented utilizing an unmodified commercial X-ray diffractometer, equipped with a Bragg–Brentano geometry, for reducing preferred orientation effects in measured intensities during quantitative diffraction analysis. The diffractometer setup examined makes possible data acquisition with Θ fixed at 1° and 2Θ scanning the Bragg line. The results obtained with this technique are shown in the quantitative X-ray diffraction analysis of three international standards of carbonate rocks (401,402,403).

The first object was to develop an X-ray diffractometric method for the detection and quantification of crystalline sucrose when it occurs as a mixture with amorphous sucrose. Standards consisting of amorphous sucrose physically mixed with 1 to 5 weight percent crystalline sucrose were prepared. The sum of the background subtracted integrated intensities of the 12.7°2θ (6.94 Å) and 13.1°2θ (6.73 Å) sucrose diffraction peaks were linearly related to the weight percent crystalline sucrose. The limits of detection and quantitation of crystalline sucrose were 0.9% and 1.8% w/w, respectively. The second object was to study the kinetics of crystallization of sucrose as a function of temperature (at 102, 105 and 110 °C under a water vapor pressure of 0 Torr) and water vapor pressure (17.4, 19.8 and 21.4 Torr at 27 °C). In all cases, the crystallization kinetics was best described by the Avrami-Erofe’ev model (three-dimensional nucleation).

The trihydrated ammonium trioxalato-chromate(III) (NH4)3 (Cr(C2O4)3)·3H2O crystallizes in the triclinic system with:

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The X-ray powder diffraction pattern for the title compound is reported in the range 10<2θ<60°. The sample was purified by recrystallization and was indexed using the program DICVOL91 and TREOR90. Refined unit parameters for the orthorhombic system (Pnma or Pn21a) are: a=13.7098(8) Å, b=10.7153(7) Å, c=6.9473(4) Å, V=1020.59 Å3, Z=4, Dx=2.50 g cm−3. M20=49, F30=93(0.0075, 43).

Experimental X-ray powder diffraction patterns and refined unit cell parameters for two barium hollandite-type compounds, BaxFe2xTi8−2xO16, with x=1.143 and 1.333, are reported here. Compared to the tetragonal parent structure, both compounds exhibit monoclinic distortions that increase with Ba content [Ba1.333Fe2.666Ti5.334O16: a=10.2328(8), b=2.9777(4), c=9.899(1) Å, β=91.04(1)°, V=301.58(5) Å3, Z=1, ρcalc=4.64 g/cc; Ba1.143Fe2.286Ti5.714O16: a=10.1066(6), b=2.9690(3), c=10.064(2) Å, β=90.077(6)°, V=301.98(4) Å3, Z=1, ρcalc=4.48 g/cc]. The X-ray powder patterns for both phases contain a number of broad, weak superlattice peaks attributed to ordering of the Ba2+ ions within the tunnels of the hollandite framework structure. According to the criteria developed by Cheary and Squadrito [Acta Crystallogr. B 45, 205 (1989)], the observed positions of the (0k1)/(1k0) superlattice peaks are consistent with the nominal x-values of both compounds, and the k values calculated from the corresponding d-spacings suggest that the Ba ordering within the tunnels is commensurate for x=1.333 and incommensurate for x=1.143. High-temperature X-ray diffraction data indicate that the x=1.333 compound undergoes a monoclinic→tetragonal phase transition between 310 and 360 °C.

The application of the Rietveld method to quantify mineral components of bauxite and lateritic samples was carried out in order to determine the ability of the method to obtain accurate mineralogical abundances for these materials. The method was initially applied to synthetic mixtures using both Cu and Co Kα radiations, and it was shown that Rietveld-derived data compared favourably with the weighed compositions. Application to two types of natural bauxite resulted in a high correlation between Rietveld predicted values and those calculated by proportioning peak intensities with chemical assays. The use of the whole pattern rather than selected peak intensities gives greater accuracy, confirmed by a strong correlation between derived oxide concentrations from XRF assays. Accuracy and precision were improved by the determination of isomorphous substitution of aluminum in goethite and hematite by refinement of unit cell dimensions. Importantly, the ability of the Rietveld program to successfully model several goethites with different levels of isomorphous substitution improved the correlation between predicted and calculated values. In addition, crystallinity and crystallite size that influence the reactivity of the mineral components can be derived from refined peak profiles.

Plant surfaces are mostly covered with microscopic layers of wax which exhibit characteristic morphologies, visible under high magnification. Waxes belonging to three different types were investigated. Powder data of seven natural and three recrystallised waxes as well as of two isolated compounds are presented. The mainly crystalline nature of the studied plant waxes is proved. The correlation between morphology, chemical composition, and powder patterns is discussed.

Metal cimetidine isothiocyanates, M(C10H16SN6)2(NCS)2, where M = Co(II), Ni(II) and Cu(II), have been investigated by means of X-ray powder diffraction. Unit cell dimensions were determined from powder diffractometer data. Refined cell parameters (monoclinic with a primitive cell), powder data, calculated densities and Z value are presented.

Considering the thermal expansion of silicon at ambient conditions, the lattice parameter will change 0.00032 Å for a 10 °C range. This range is measurable with modern diffraction instrumentation illustrating the importance of knowing the accurate lattice parameter, the temperature of measurement, and the thermal expansion coefficient. The best value for the expansion coefficient is 2.45×10−6/°C.

The incommensurately modulated structure of Bi2Sr2Eu1.3Ce0.7Cu2O10.17, with a = 5.4752(4) Å, b = 5.4522(3) Å, c = 17.860(1) Å, Z = 2, was refined by the GJANA program [Gao et al., Acta Cryst. A 49, 141 (1993)] from X-ray powder data in C:C2mb: 111 four-dimensional space group (Rov = 0.064, Rm = 0.041, Rsat = 0.202, Rp = 0.049, Rwp = 0.065). Displacive modulation parameters of all cations and oxygen atoms in the Bi-layer were involved in the refinement. Obtained results including the modulation parameters are in agreement with those found for the similar phase Bi2Sr1.7Nd1.8Ce0.5Cu2O10+δ from single-crystal data [Mironov et al., J. Solid State Chem. 109, 74 (1994)].

A resident powder diffractometer control program is described, which allows independent use of the PC for other programs during data collection. The control program and a simple interface card were developed for the case when a PC is used to automate the DRON type diffractometers.