The effect of phosphate on the formation of Fe oxides from Fe(II) salts is important because phosphate is a ubiquitous anion in natural environments. For this reason, the products formed by oxidation of phosphate-containing Fe(II)SO4 solutions neutralized with bicarbonate were characterized. The rate of oxidation of Fe(II) increased with increasing P/Fe atomic ratio to 0.2 in the initial solution. Goethite (α-FeOOH) or lepidocrocite (γ-FeOOH) or both were produced and identified by powder X-ray diffraction (XRD). The ratio between lepidocrocite and goethite increased with increasing P/Fe. In the 5–8.5 pH range, the formation of goethite predominated at P/Fe < 0.005, but only lepidocrocite was detected by XRD for P/Fe > 0.02. Thus, phosphate favors lepidocrocite formation because lepidocrocite has (1) a layered structure (like its precursor green rust), and (2) a structure less dense than that of goethite, thereby requiring less complete removal of the green-rust interlayer phosphate to form. The lepidocrocite crystals were platy, with prominent {010} faces and the thickness of the plates decreased with increasing P/Fe from >25 nm for P/Fe < 0.005 to <5 nm for P/Fe > 0.1. The solubility of lepidocrocite in acid oxalate was nearly complete for P/Fe > 0.03. The lepidocrocite contained occluded phosphate, i.e., phosphate that could not be desorbed by alkali treatment. The decrease in the b unit-cell length with increasing P/Fe suggests that lepidocrocite may contain structural P.

Thirty six bentonite samples from 16 different locations were examined in order to demonstrate the applicability of a new Rietveld description approach for quantitative phase analysis. X-ray diffraction patterns of the bulk material were obtained and analyzed by the Rietveld method. The samples contain up to ten different minerals, with dioctahedral smectite as the major component. A model for turbostratic disorder of smectites was formulated inside a structure-description file of the Rietveld program BGMN. The quality of the refinements was checked using an internal standard mineral (10.0 or 20.0 wt.% corundum) and by cross-checking results with X-ray fluorescence (XRF) data. The corundum content was reproduced with only small deviations from the nominal values. A comparison of the chemical composition obtained by XRF and the composition as re-calculated from quantitative Rietveld results shows a satisfactory agreement, although X-ray amorphous components such as volcanic glasses were not considered. As a result of this study, the Rietveld method combined with the new structure model for turbostratic disorder has proven to be a suitable method for routine quantitative analysis of bentonites with smectites as the dominant clay minerals.

Sediments from the ST5 deep-sea bottom core collected from the south-east Aegean Sea between Symi and Tilos islands, Greece, were examined by quantitative mineralogical analysis and geochemical analysis to infer provenance and palaeoenvironmental control over sediment deposition. The mineralogical composition comprises carbonates (mainly calcite and Mg-calcite), quartz, feldspars, serpentine, amphibole and clay minerals. Chlorite is the most abundant clay mineral, whereas smectite and illite are less abundant than in the sediments in the south-west Aegean and the Cretan Sea. Semi-quantitative analysis of clay minerals from oriented clay fractions overestimates significantly the smectite content and underestimates the abundances of illite, chlorite and kaolinite. The studied sediments are enriched in MgO, Ni and Cr, which decrease in abundance with decreasing depth, following the distribution of serpentine. By contrast, the abundances of SiO2, Al2O3, Fe2O3, Na2O and K2O increase upcore. The regional S1 sapropel horizon is enriched in V and Co and has considerably greater Ba/Al ratios than the remaining sequence. The mineralogical and geochemical relationships indicate a strong ultrabasic influence, probably from the Marmaris ophiolite in the Lycian nappes. The clay mineral distribution suggests that the smectite was mainly of volcanogenic origin, the illite was supplied by the nearby landmasses of west Anatolia and the islands of Rhodes, Tilos and Symi and the contribution from the south-east Mediterranean was limited or totally lacking. The combined use of the mineralogical and geochemical analysis of bulk sediments rather than the clay fractions is not only extremely useful in tracing sediment provenance in relatively closed basins, but it also enables a more realistic assessment of the importance of water circulation patterns on sedimentation processes in such environments.

X-ray diffraction is used widely for quantitative analysis of geological samples but studies which document the accuracy of the methods employed are not numerous. Synthetic sandstones of known composition are used to compare a ‘routine application’ of a Rietveld and a reference intensity ratio (RIR) method of quantitative phase analysis. Both methods give similar results accurate to within ~±3 wt.% at the 95% confidence level. The high degree of accuracy obtained is believed to depend to a large extent on the spray-drying method of sample preparation used to eliminate preferred orientation.

A synthetic analogue, Ca(Ti0.6Al0.2Ta0.16Nb0.04)OSiO4, of an aluminoan tantalian titanite previously described from Craveggia pegmatite (Piemonte, Italy) has been prepared by a ceramic synthesis technique and its crystal structure determined by Rietveld analysis of the powder X-ray diffraction pattern. The synthetic Al-Ta-Nb-rich titanite adopts space group A2/a implying that substitutions at the single octahedral site destroy the coherence of the off-centering of octahedral chains in the titanite structure resulting in a P 21/a → A2/a phase transition. Unit-cell dimensions obtained for the Al-Ta-Nb-rich titanite are: a = 7.0649(1) Å; b = 8.7187(1) Å; c = 6.5701(1) Å; β = 113.755(1)°, V = 370.41(1) Å3. The extensive replacement of Ti by Al, Ta and Nb results in a considerable decrease in the distortion of all coordination polyhedra in the structure of this titanite. These structural data suggest that a solid solution CaTi1-x(Alx /2 [Ta,Nb]x /2)OSiO4 (0 ≤ x ≤ 0.4) adopting the titanite structure might exist.

The crystal structure of the displacive ferroelectric mineral russellite, Bi2WO6, has been determined using Rietveld profile refinement of high-resolution, time of flight, neutron powder diffraction data on the synthetic compound. Russellite is orthorhombic, Pca21, with a 5.43726(2) Å, b 16.43018(5) Å, c 5.458422) Å, Z = 4 and is isostructural with the bismuth molybdate mineral koechlinite, Bi2MoO6. The structure consists of layers of tilted WO6 octahedra sandwiched between layers of bismuth and oxygen with the tungsten displaced from the centre of the octahedron by 0.278 Å. The orientations of the lone-pair electrons in the Bi3+ cations have been inferred from the 3.0 Å coordination shells of both crystallographically independent bismuths, and have been found to be non-centrosymmetric, an effect which may give rise to the tilting of the WO6 octahedra. New laboratory source X-ray powder diffraction data are presented for russellite, which, with supplementary synchrotron powder diffractometry, corroborate the new space group and structure determination.

The structure of a synthetic end-member wairakite (CaAl2Si4O12·2H2O) has been determined using Rietveld analysis of high-resolution, synchrotron X-ray powder diffraction data, and 29Si and 27Al magic angle spinning nuclear magnetic resonance spectroscopy. The framework in the synthetic sample is more disordered than that in natural wairakite. Ca is distributed over the cavity cation sites M2, M12A, M12B in the approximate proportions 0.8:0.1:0.1, respectively, with M11 being vacant. 29Si MAS NMR data are consistent with about 80% of the Si occupying tetrahedral T11 and T12 sites linked to two Al atoms [Q4(2Al) silicons]. Tetrahedral and cavity cation site disorder are coupled so that Al mainly occupies T2 sites, with Ca in M12A and M12B being balanced by Al in T12A and T12B; T11A and T11B sites appear to only contain Si, in agreement with the M11 site being vacant. The crystal chemistries of the wide range of stoichiometries which crystallize with the leucite/pollucite structure-type are also reviewed, with particular attention being paid to the tetrahedral ordering configurations present in these phases, and the implications to crystallographic phase transitions.

Commercial anodes with different state of charge are investigated by X-ray diffraction technique using Rietveld method for data collected with standard laboratory equipment. It is shown that full profile refinement gives good approximation for quantitative description of the charge/discharge process and may be used for estimation of real state of charge (SoC). Careful analysis of the diffraction profile with Rietveld method allows us to quantitatively distinguish the contribution of different LixC6 phases and estimate the real SoC.

Structures of the two M0.50SbFe(PO4)3 (M = Mg, Ni) phases, abbreviated as [Mg0.50] and [Ni0.50], were determined at room temperature from X-ray diffraction (XRD) powder data using the Rietveld analysis. Both compounds belong to the NASICON structural family. XRD patterns of [Mg0.50] and [Ni0.50] phases were easily indexed with a primitive hexagonal unit cell [P$\overline 3 $ space group, Z = 6] similar to that already obtained for La0.33Zr2(PO4)3. Obtained unit cells parameters are [a = 8.3443(1) Å, c = 22.3629(1) Å], and [a = 8.3384(1), c = 22.3456(1) Å], respectively, for [Mg0.50] and [Ni0.50] phosphates. In both samples, the [Sb(Fe)(PO4)3]− NASICON framework is preserved and a partially-ordered distribution of Sb5+ and Fe3+ ions is observed. Raman spectroscopic study was used to obtain further structural information about the nature of bonding in [Mg0.50] and [Ni0.50] phases.

The General Structure and Analysis Software II (GSAS-II) package is an all-new crystallographic analysis package written to replace and extend the capabilities of the universal and widely used GSAS and EXPGUI packages. GSAS-II was described in a 2013 article, but considerable work has been completed since then. This paper describes the advances, which include: rigid body fitting and structure solution modules; improved treatment for parametric refinements and equation of state fitting; and small-angle scattering data reduction and analysis. GSAS-II offers versatile and extensible modules for import and export of data and results. Capabilities are provided for users to select any version of the code. Code documentation has reached 150 pages and 17 web-tutorials are offered.

CaTi1−xSnxO3 (x = 0.0–1.0) solid solutions were prepared by solid-state reaction at 1450 °C. Rietveld refinement of their powder X-ray diffraction patterns revealed that all the solid solutions crystallized in orthorhombic cells with the perovskite-type structure, the space group Pbnm. The refined unit-cell parameters linearly increased with nominal tin contents x.

Crystallographic structures of the three NaSbR(PO4)3 (R = Cr, Fe, In) phases were determined at room temperature from X-ray powder diffraction (XRD) data using the Rietveld analysis. The three compounds belong to the Nasicon structural family. The presence of the (303) reflection in all XRD spectra of NaSbR(PO4)3 shows clearly that all compounds crystallise in rhombohedral system with R3 space group. Na atoms are practically ordered within the two positions, 3a and 3b, of M1 sites. Structure refinements show also a partially-ordered distribution of Sb5+ and R3+ ions within the Nasicon framework. A Raman and Infrared spectroscopic study was used to obtain further structural information about the nature of bonding in NaSbR(PO4)3 (R = Cr, Fe, In) phases.

In order to exploit X-ray powder spectro-diffractometry, the program RIETAN-97ß for refining crystal structure and lattice parameters by the Rietveld method was modified extensively. The resulting software can be used to refine anomalous scattering factors, fr and fi, for specified crystallographic sites near the X-ray absorption edge of a particular element. The effectiveness of the modified software was tested by using powder diffraction patterns simulated by the original RIETAN-97ß software and a series of measured powder diffraction patterns of Fe3O4 with incident X-ray energies near the absorption edge of iron.

A new semi-empirical approximation for the asymmetry function to be used in the X-ray Rietveld analysis has resulted in lower values of the so-called goodness-of-fit index, defined as S = Rwp/Rexp, where Rwp is the R-weighted pattern and Rexp is the R-expected [R. A. Young, The Rietveld Method (Oxford U.P., Oxford, 1993)], with respect to the corresponding values obtained with the classical approximation used by Rietveld in his fundamental paper. A comparing test of the two asymmetry functions was carried out for the cubic Y2O3 and for αAl2O3 using either pseudo-Voigt or Pearson VII symmetrical functions and two diffractometers. As in the case of the Rietveld approximation, the present one, which employs an exponential function, is optimized using only one fitting parameter. Experimentally, the asymmetry can be considerably diminished by using Soller slits with a small opening angle (≤2°).

The powder pattern of calcium galactarate tetrahydrate (CaC6H8O8·4H2O) is presented. The compound was found in white wine stored for 4 years. A Rietveld refinement using the atomic coordinates from a single crystal study as starting values was refined with 55 parameters and without preferred orientation to RB=5.97%, RF=4.44%, Rp=10.39%, and Rwp=13.43% for 84 reflections. Crystal data: Mr=320.14, orthorhombic, Pcan, a=7.3359(1) Å, b=11.6296(3) Å, c=15.0978(6) Å, V=1288.05(6) Å3, Z=4, Dx=1.651 g/cm3, λ(CuKα1)=1.54060 Å, μ=46.76 cm−1.

The room temperature X-ray powder diffraction pattern of Fe2GeSe4, a II2 □ IV VI4 semiconducting compound, has been recorded and evaluated. This material was found to be orthorhombic, a=13.069(1), b=7.559(1), c=6.2037(6) Å, V=612.83(9) Å3, Z=4, Dx=5.42 gcm−3. The structure refinement carried out using the Rietveld method indicated that this material crystallizes in space group Pnma (No. 62) with an olivine type of structure. The refinement of 33 parameters led to RWP=15.3%, RP=10.2% for 5251 step intensities and RB=9.44% and RF=9.36% for 913 reflections.

Ab initio structure determination of new compound (Pb0.6Cu0.4)Sr2PrCu2O7−x was obtained at 300 and 100 K from X-ray powder diffraction data and refined by Rietveld technique. (Pb0.6Cu0.4)Sr2PrCu2O7−x has an isotypical structure with TlBa2CaCu2O7 (1212) at both 300 and 100 K. At 300 K, crystal data: (Pb0.522Cu0.4)Sr2PrCu206.53, Mr=681.293, tetragonal system, space group P4/lmmm, a = 3.8631(5)Å, c= 11.9134(2)Å, V= 177.79Å3, Z= 1, Dx, = 6.3631 g/cm3, μ=1036.549 cm−1 (λ=1.54051 Å), F(000) = 299.6, the structure was refined with 31 parameters to Rwp = 4.02%, Rp=2.96% for 3379 step intensities and Rb = 4.80%, Rf=5.17 for 143 reflections, “goodness of fit” S = 2.20. At 100 K, crystal data: (Pb0.547Cu0.4)Sr2PrCu2O6.89, Mr=692.232, tetragonal system, space group P4/mmm, a = 3.8580(2) Å, c= 11.8898(5) Å, Z=1, Dx = 6.4953 g/cm3, μ= 1053.235 cm−1 (λ=1.54051 Å), F(000) = 304.6, the structure was refined with 32 parameters to Rwp = 5.53%, Rp=4.22% for 2574 step intensities and Rb = 6.11%, Rf=5.31% for 111 reflection, “goodness of fit” S= 1.79. Moreover, the composition of Pb was refined to 0.522 at 300 K and to 0.547 at 100 K as compared with the stoichiometric composition 0.6.

Three computer programs for Rietveld analysis DBWS-9411, HILL-93.06, and FULLPROF-3.1 have been tested and compared using data for two samples of different complexity, spinel, and anglesite. The investigation shows that results are “program dependent.” The obtained R indices for spinel are in the ranges 10.60%–13.26%(Rwp) and 3.15%–5.25%(RB). Similarly, the ranges for anglesite are 9.76%–14.06%(Rwp) and 2.15%–5.06%(RB). Some atom and displacement parameters are significantly different, too. In attempt to define the standard procedure for Rietveld analysis, three parameters, n, BKPOS, and RLIM were examined. It was found that the most appropriate values for them are: n=8–10, BKPOS=90°, and RLIM=40° 2θ. Using Fourier filtering for background modeling, significantly lower R indices were obtained in comparison to polynomial and interpolated background. At the same time the great numbers of atom and cell parameters agree within ±3σmax and e.s.d.'s were identical or lower than those achieved for polynomial and interpolated background. It was found that the function given by Bérar and Baldinozzi (1993) (J. Appl. Crystallogr. 26, 128–129) much better described asymmetric peak profiles at low 2θ angles. This function and Fourier filtering were implemented only in FULLPROF, which has more possibilities and some advantages over the other two programs. In addition, the peak shift parameters (sample displacement and transparency) were tested. It was shown that under present circumstances these parameters do not have much effect on atom parameters and R indices. However, differences in unit cell parameters were considerable greater, most probably because of the large correlation between zero-point, lattice, and peak shift parameters.

Indexed X-ray powder diffraction data are reported for two organic salts with carbon rings having two quaternary nitrogens: diazonia-6,9 dispiro [5.2.5.2] hexadecane and diazonia-6,9 dispiro [5.2.5.3] heptadecane diiodides. For these compounds, which give solid electrolytes when associated with AgI, powder diffraction diagrams calculated by the Rietveld method from single crystal structure determinations are presented and are compared to the experimental diffraction data.

The crystalline structure of new TlSr2PrCu207−x was obtained at room temperature (300 K) and low temperature (100 K) from X-ray powder diffraction with CuKα radiation using Rietveld analysis. TlSr2PrCu207−x has an isotypical structure with TlBa2CaCu207 (1212). At 300 K, crystal data: Tl0.864Sr2PrCu2O6.75, Mr=727.811, the tetragonal system, P4/mmm, a =3.85404(5) Å, c = 12.1046(2) Å, V=179.80 Å3, Z=1, Dx =6.7218 g cm−3, μ =1143.922 cm−1 (λ = 1.54051 Å), F(000)=317.0, the structure was refined with 28 parameters to Rwp=5.29%, Rp = 3.65% for 3551 step intensities and Rb=7.40%, Rf=639% for 155 peaks, “goodness of fit” 5=3.05. At 100 K, crystal data: Tl0.858Sr2PrCu2O6.61, Mr=724.345, the tetragonal system, P4/mmm, a =3.84872(6) Å, c = 12.0771(3) Å, V=178.89 Å3, Z=1, Dx=6.7235 g cm−3, μ=1146.939 cm−1 (λ= 1.54051 Å), F(000) = 315.4, the structure was refined with 26 parameters to Rwp=6.70%, Rp=5.11% for 2926 step intensities and Rb=7.83%, Rf=6.70% for 131 peaks, “goodness of fit” S = 1.75.