Development of preferred orientations of illite-smectite (I-S) has been studied using X-ray diffraction (XRD) texture goniometry to produce pole figures for clay minerals of a suite of 16 mudstone samples from a core from the Gulf Coast. Samples represent a compaction-loading environment in which the smectite-to-illite (S-I) transition occurs. In five shallow, pre-transition samples, there is no significant preferred orientation for smectite-rich I-S. Development of preferred orientation of I-S, although weak, was first detected at depths slightly less than that of the S-I transition. The degree of preferred orientation, which is always bedding-parallel, increases rather abruptly, but continuously, over a narrow interval corresponding to the onset of the S-I transition, then continues to strengthen only slightly with increasing depth. The degree of post-transition preferred orientation is also dependent on lithology, where the preferred orientation is less well-defined for quartz-rich samples.

Previously obtained transmission electron microscope (TEM) data define textures consistent with the change in orientation over many crystallites. The smectite in pre-transition rocks consists largely of anastomosing, “wavy” layers with variable orientation and whose mean orientation is parallel to bedding, but which deviate continuously from that orientation. This results in broad, poorly defined peaks in pole figures. Post-transition illite, by contrast, consists of thin, straight packets, with most individual crystallites being parallel or nearly parallel to bedding. This results in pole figures with sharply defined maxima. By analogy with development of slaty cleavage in response to tectonic stress during metamorphism, the S-I transition is marked by dissolution of smectite and neocrystallization of illite or I-S locally within the continuous “megacrystals” of smectite. The transition is inferred to have some component of mechanical rotation of coherent illite crystals within a pliant matrix of smectite. The data suggest that change in orientation and coalescence of clay packets plays an important role in the formation of the hydraulic seal required for overpressure generation.

Investigation of a naturally occurring mixture of dioctahedral micas prompted an examination of X-ray diffraction (XRD) techniques for obtaining quantitative estimates of 1M and 2M 1 mica proportions. A method for determining quantitative estimates has been developed that includes the effect of preferred orientation of mica particles as described by the March function. A diagram is presented from which the percentage of 2Mı and the March parameter (r) can be obtained from two peak-area ratios: 2.80 Å/5.0 Å and 2.80 Å/2.58 Å, which are measured on observed XRD patterns of mica mixtures. The ability of this peak-area ratio diagram to predict reasonably accurate proportions of 1M and 2Mı micas was tested by comparing calculated and observed XRD patterns over a range of 2θ values from 16° to 40° for size-fractionated mixtures. Lack of accurate crystal-structure data for dioctahedral 1M mica proved an impediment to obtaining improved quantitative estimates of mica proportions.

NEXAFS is shown to be an excellent technique, of potentially widespread application, for the determination of the orientation of organic molecules intercalated in preferentially oriented thin films of polycrystalline, layered minerals. A NEXAFS study of [Mg2Al(OH)6]+C7H5O2 · nH2O, a layered anionic clay, is described. This material shows a transition from a layer spacing of 15.4 Å to only 9 Å at a remarkably low temperature (below 100°C). This is shown to be accompanied by a change in the angle of the plane of the benzoate molecule to the 00ℓ planes from 35° ± 10° to 0° ± 10°. The tilt of the benzoate anion in the room temperature structure demonstrates the presence of an interaction between the phenyl ring and the positively charged, brucite-like layers. Furthermore it is suggestive of the importance of hydrogen bonding in determining the interlayer spacing and stability.

In X-ray diffraction (XRD) analysis, preparation of oriented clay specimens enhances their 00l reflections by arranging basal surfaces parallel to the specimen surface. In one-dimensional modeling of XRD intensities, degree of preferred orientation is one of the variable parameters and a user may choose different σ* values for different minerals. The usual assumption is, however, that the layers of all clay minerals that are present exhibit a similar degree of preferred orientation to that of the clay mineral flakes parallel to the basal plane. If the orientation of individual clay minerals is significantly different, and if this is not taken into account, the relative proportions of the constituent minerals cannot be modeled accurately. The actual or so-called ‘preferred’ orientation is a potentially large source of error in any attempt at quantitative XRD analysis because it cannot be assumed to be constant among different minerals and may also vary as a result of pretreatment. In the present study the influence of sample composition and sample pretreatment on the degree of preferred orientation was determined using the parameter σ*. A statistical parameter was calculated to determine and ensure the reproducibility of σ* measurements. The most important result was that, when mixed together, clay minerals influence each other in terms of the degree of preferred orientation. Among individual samples, the degree of preferred orientation can be different for each clay mineral. The power of sonication used in sample pretreatment of a pure kaolinite and a pure illite had no significant influence on the degree of preferred orientation. The changes in intensities upon variation of the tilting angle (χ) allowed for calculation of σ* of smectites in pure samples, in admixtures, and in samples treated in two different ways (air-dried and glycerol-intercalated), which is reported here for the first time. Smectites are very fine grained with flexible morphology which is believed to be the reason for their tendency to exhibit poor orientation (σ* = 22°); further research is required to establish whether this is a general feature of smectites. After glycerol treatment a soil smectite showed a slightly better orientation compared to the air-dried pattern. The results of the study illustrate the difficulty of predicting changes in preferred orientation of clay mineral admixtures, even if non-platy minerals such as clay-sized quartz are added. In general, σ* decreased when non-platy minerals were added, which is explained by changes in geometry of the specimen. Not all clay minerals, however, showed simultaneous changes in their orientation behavior.

The thermal maturity of samples of the Posidonia Shale collected from the Hils Syncline, northern Germany, varies significantly as a function of location indicating variations in local history. Synchrotron X-ray diffraction was used to document the composition and the preferred orientation of four samples of the Posidonia Shale with different degrees of maturity (0.68–1.45%, Ro) to determine possible effects on diagenesis and preferred orientation. Overall, the degree of preferred orientation of all clay minerals (illite-smectite, illite-mica, and kaolinite) and in all samples is similar, with (001) pole figure maxima ranging from 3.7 to 6.3 multiples of a random distribution (m.r.d.). Calcite displays weak preferred orientation, with c axes perpendicular to the bedding plane (1.1–1.3 m.r.d.). Other constituent phases such as quartz, feldspars, and pyrite have a random orientation distribution. The difference in thermal history, which causes significant changes in the maturity of organic matter, influenced the preferred orientation of clay minerals only marginally as most of the alignment seems to have evolved early in their history. Synchrotron X-ray microtomography was used to characterize the three-dimensional microstructure of a high-maturity sample. Low-density features, including porosity, fractures, and kerogen, were observed to be elongated and aligned roughly parallel to the bedding plane. The volume of low-density features was estimated to be ~7 vol.%, consistent with previous petrophysical measurements of porosity of 8–10 vol.%. Transmission electron microscopy analysis of samples with different degrees of maturity (0.74%Ro and 1.45%Ro) was used to document microstructures at the nanoscale as well as the presence of kerogen. In the high-maturity sample, pores were less abundant while minerals were more deformed as shown by fractured calcite and by kinked and folded illite. Some of the porosity was aligned with clay platelets.

Anisotropy in clay-rich sedimentary rocks is receiving increasing attention. Seismic anisotropy is essential in the prospecting for petroleum deposits. Anisotropy of diffusion has become relevant for environmental contaminants, including nuclear waste. In both cases, the orientation of component minerals is a critical ingredient and, largely because of small grain size and poor crystallinity, the orientation distribution of clay minerals has been difficult to quantify. A method is demonstrated that relies on hard synchrotron X-rays to obtain diffraction images of shales and applies the crystallographic Rietveld method to deconvolute the images and extract quantitative information about phase fractions and preferred orientation that can then be used to model macroscopic physical properties. The method is applied to shales from European studies which investigate the suitability of shales as potential nuclear waste repositories (Meuse/Haute-Marne Underground Research Laboratory near Bure, France, and Benken borehole and Mont Terri Rock Laboratory, Switzerland). A Callovo-Oxfordian shale from Meuse/Haute-Marne shows a relatively weak alignment of clay minerals and a random distribution for calcite. Opalinus shales from Benken and Mont Terri show strong alignment of illite-smectite, kaolinite, chlorite, and calcite. This intrinsic contribution to anisotropy is consistent with macroscopic physical properties where anisotropy is caused both by the orientation distribution of crystallites and high-aspect-ratio pores. Polycrystal elastic properties are obtained by averaging single crystal properties over the orientation distribution and polyphase properties by averaging over all phases. From elastic properties we obtain anisotropies for p waves ranging from 7 to 22%.

The alignment of phyllosilicates in clays has received a lot of attention because it is a major cause of seismic anisotropy in the Earth’s crust. Thus far, all attention has been on shales where the orientation pattern has been attributed to compaction and observed to increase with burial depth and diagenetic processes. Here, for the first time, the same methods that were developed to quantify shale preferred orientation were applied to clays forming in surface environments, a seasonal streambed in Death Valley, California; a mudpool from mud volcanoes in Imperial Valley, California, close to the Salton Sea; and a glacial lake from Val Albigna in the Swiss Alps. Preferred orientation was analyzed quantitatively with high-energy synchrotron X-ray diffraction. All three samples showed strong alignment of phyllosilicates with (001) pole figure maxima 2–4 multiples of a random distribution, comparable to shales, and indicating that significant preferred orientation can be produced at surface conditions. The original alignment during sedimentation may be an important factor for the final microstructure in many shales.

This paper describes an improved simple, sample-mounting method for random powder X-ray diffraction (XRD), namely the razor tamped surface (RTS) method, which prepares a powder mount by tamping the loose powder with the sharp edge of a razor blade. Four kaolinites and a quartz powder were used to evaluate the RTS method by quantifying the degree of orientation in the sample mounts using orientation indices. Comparisons between the RTS and other published simple methods, consisting of front loading, back loading and side loading, indicate that the RTS method produces minimum packing density and minimum preferred orientation in the powder mounts of all five samples. The quartz powder used in this study does exhibit a tendency to preferred orientation. The mechanism by which the RTS method reduces preferred orientation is examined by comparing the width of the sharp blade edge with the size of clay particles. The advantages and disadvantages of the RTS method are also discussed.

X-ray powder diffraction data, unit-cell parameters, and space group for the Lumateperone tosylate, C24H29FN3O⋅C7H7O3S, are reported [a = 15.5848(10) Å, b = 6.0700(4) Å, c = 31.3201(14) Å, β = 96.544(5)°, V = 2943.58 Å3, Z = 4, and space group C2]. In each case, all measured lines were indexed and were consistent with the corresponding space group. The single-crystal data of Lumateperone tosylate is also reported, respectively [a = 15.626(3) Å, b = 6.0806(10) Å, c = 31.415(5) Å, β = 96.609(7)°, V = 2965.1(8) Å3, Z = 4, and space group C2]. The experimental powder diffraction pattern has been well matched with the simulated pattern derived from the single-crystal data with preferred orientation in the [002] direction (orientation coefficient = 0.75).

Least-squares analysis on the diffraction intensity values certified for NIST SRM676a and SRM1976c α-Al2O3 (corundum) have shown that the intensities of SRM1976c can be simulated by the March-Dollase preferred orientation model along the (001)-direction. Diffraction intensities of randomly oriented corundum crystallites have been calculated from electron density data obtained by conventional and density functional theory (DFT) calculations, on the assumption of independent and similar atomic displacements for Al and O atoms. The results of DFT calculations support that the strongest peak of randomly oriented α-Al2O3 crystalline powder should be 113-reflection, though the intensities simulated by DFT calculations are not closer to NIST SRM676a intensities than those expected for a fully ionized model ${\rm Al}_2^{3 + } {\rm O}_3^{2-}$. Diffraction data of two types of relatively fine (nominally 2–3 μm and ca 0.3 μm) α-Al2O3 powder have been collected and processed by a deconvolutional treatment (DCT). Integrated peak intensities extracted from the DCT data by an individual peak profile fitting method also support that the 113-reflection is the strongest reflection of randomly oriented α-Al2O3 crystalline powder.

Neutron diffraction texture goniometry indicates that naturally deformed polycrystalline pyrite ores from Mt. Lyell (Tasmania) and Degtiarka (Ural Mountains) have weak lattice preferred orientations. During experimental deformation involving dislocation flow at elevated temperatures and pressures, these initial fabrics have been modified to produce new lattice preferred orientations.

Polycrystalline pyrite form Mt. Lyell (B-1) has an initial <111> - fibre texture perpendicular to a grain-size layering. After 24% shortening perpendicular to the <111> - fibre axis at 700°C a new, but weak <100> texture has developed parallel to the shortening axis. The Degtiarka pyrite (PN-6) initially has two weak fibre components. The somewhat stronger component is a <100>-fibre texture, similar to that in the experimentally deformed B-1 pyrite. The other one is a <111> - fibre texture similar to the intital B-1 preferred orientation. After 30% shortening oblique to both initial fibre axes at 600°C weak <110>- and <111>-fibre textures have developed. The experimentally produced fabrics have developed during deformation involving dislocation flow, dynamic recrystallisation and some microcracking. Intergranular sliding may also have been involved. Differences between lattice preferred orientations developed in the 600°C and 700°C experiments are interpreted to indicate a change in the dominant flow mechanism with changing temperature.

In comparison with other cubic minerals that have been deformed experimentally by dislocation flow mechanisms, the pyrite shows an unusually weak preferred orientation which can be detected only by means of neutron diffraction texture goniometry.

Chalcopyrite samples from Mt Isa, Australia have been experimentally shortened by up to 30% at temperatures up to 450°C at a constant confining pressure of 300 (400) MPa, and different strain rates in the range from 10-5 to 10-8 sec-1. After deformation, the X-ray pole figures show a maximum of (220/204) perpendicular to the compression axis for each of the samples, which has already been described for room temperature experiments by Lang (1968). The overlapping pseudocubic peaks of chalcopyrite can be separated into true tetragonal peaks by neutron diffraction texture analysis using a position sensitive detector combined with profile analysis (Will et al., 1989). The five investigated samples each show a combination of two or four main orientations of the crystallites, which represent neither a pseudocubic nor a tetragonal fibre texture.

X-ray powder diffraction data, unit-cell parameters, and space group for acetamidinium formate, C3H8N2O2, are reported [a = 6.4564(5) Å, c = 13.021 (3) Å, unit-cell volume V = 542.8(3) Å3, M.p. = 215(1)°C, ρc = 1.274 g.cm−3, ρm = 1.269 g.cm−3, Z = 4, and space group P43212]. The front-loaded technique got sample with strong preferred orientation because of plate-like shape of crystallites, so the capillary packing was used for final powder data collection. All measured lines were indexed and are consistent with the P43212 space group. No detectable impurities were observed.

Two series of zirconium samples were investigated by neutron and X-ray diffraction. First series of the samples was deformed at room temperature (RT), whereas the second series was deformed at 300 °C. Both series were deformed on uniaxial tensile machine INSTRON 5882 from strain 0 to 30% (strain step was 5%). The neutronographic texture measurements were performed on the KSN-2 neutron diffractometer located at the research reactor LVR-15 in the Nuclear Research Institute, plc. Rez, Czech Republic. The X-ray measurements were performed at the theta/theta X'Pert PRO diffractometer with the Cr X-ray tube. Observed data were processed by the software packages GSAS and X'Pert Texture. Preferential orientation of the $\left({10\bar 10} \right)$ and $\left({11\bar 20} \right)$ plane poles is found to be parallel to the rolling direction for both tested deformation series. Poles of the $\lpar 10\bar 12\rpar $ and $\lpar 10\bar 13\rpar $ planes tend to be parallel to the normal direction (Tables II and III). Orientation of the basal poles is tilted by 45° from the normal direction toward the transverse direction. Sharpness of the resulting texture increases with extends of the applied deformation as well as with rise of the tensile test temperature from the RT level to 300 °C.

Diffraction data of calcite were collected using a conventional Bragg–Brentano diffractometer, which is a convenient, low-cost, and highly popular in-house instrument, and its crystal structure was refined by the Rietveld method. This paper shows how one treats preferred orientation and how different refinement strategies affect the accuracy of the result.

Palmierite (K2Pb(SO4)2) has been prepared via a chemical synthesis method. Intensity differences were observed when X-ray powder data from the newly synthesized compound were compared to the published powder diffraction card (PDF) 29-1015 for Palmierite. Investigation of these differences indicated the possibility of preferred orientation and/or chemical inhomogeneity affecting intensities, particularly those of the basal (00l) reflections. Annealing of the Palmierite was found to reduce the effects of preferred orientation. Electron microprobe analysis confirmed K:Pb:S as 2:1:2 for the for the annealed Palmierite powder. Subsequent least-squares refinement and Rietveld analysis of the annealed powder showed peak intensities very close to that of a calculated Palmierite pattern (based on single crystal data), yet substantially higher than many of the PDF 29-1015 published intensities. Further investigation of peak intensity variation via calculated patterns suggested that the intensity discrepancies between the annealed sample and those found in PDF 29-1015 were potentially due to chemical variation in the K2Pb(SO4)2 composition. X-ray powder diffraction and crystal data for Palmierite are reported for the annealed sample. Palmierite is trigonal/hexagonal with unit cell parameters a=5.497(1) Å, c=20.864(2) Å, space group R-3m(166), and Z=3.

Polycrystalline lead iodide, PbI2, was recrystallized from hot water to reproducibly obtain flat plate-like crystals, which manifested extreme preferred orientation greatly favoring the 001, 002, 003, and 004 planes. Polycrystalline samples of PbI2 were intercalated with tripropylamine, simultaneously producing a “new” intercalate 001 peak at 7.791°2θ (d=1.1347 nm) and diminishing the host PbI2 001 peak at 12.67°2θ (d=0.6980 nm). This is consistent with large increases in the c direction of the unit cell associated with inserting a guest between adjacent iodide layers of the host PbI2. Experimental powder diffraction results are compared to theoretical values calculated using CRYSTALMAKER and CRYSTALDIFFRACT software

CdTe thin films were grown on indium tin oxide glass substrates by a closed-space sublimation method using a resistor heater. Crystalline structure, morphology, and band gaps of the films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical absorption, respectively. The XRD analysis showed that the textures of the films were found to depend on the rate of increase in the heating current. The CdTe thin film had an (111) texture when the heating current rate was 2.0 A/min. The SEM analysis revealed that the film is composed of polyhedral grains of microns size. However, the (111) texture of the CdTe thin film observed by XRD decreased with the appearance of (220), (311), (400), (331), (422), and (511) peaks of the fcc CdTe phase when the heating current rate increased to 4.5 A/min. The (111) texture disappeared when the heating current was increased immediately from 0 A to the target current of 70 A. SEM results revealed that the grains in the film are round and the grain size is smaller than 1 μm. Optical absorption analysis showed that there is no distinctive difference in the band gaps of the films.

Preferred orientation or texture is a common feature of experimental powder patterns. The mathematics of two commonly used models for preferred orientation—the March-Dollase and the generalized spherical-harmonic models—is reviewed. Both models were applied individually to neutron powder data from uniaxially pressed molybdite (MoO3) and calcite (CaCO3) powders in Rietveld analyses, as well as the as-received powders. The structural refinement results are compared to single-crystal structures. The results indicate that reasonable refinement of crystal structures can be obtained using either the March model or generalized spherical-harmonic description. However, the generalized spherical-harmonic description provided better Rietveld fits than the March model for the molybdite and calcite. Therefore, the generalized spherical-harmonic description is recommended for correction of preferred orientation in neutron diffraction analysis for both crystal structure refinement and phase composition analysis. Subsequently, the generalized spherical-harmonic description is extended to crystal structure refinement of annealed and the aged polycrystalline Ni-rich Ni50.7Ti49.30 shape memory alloys.

Striate cortical cells were classified according to whether or not their preferred orientation was close to one of the “primary” orientations (horizontal, vertical or radial, i.e. directed to the area centralis) and according to their ordinal position on the afferent pathway from the dorsal lateral geniculate nucleus (dLGN). Among the neurones that could be driven monosynaptically from the dLGN, there was a high representation of those with a preference for the primary orientations. This was particularly evident in the case of C (complex) cells. There was no such preponderance of primary orientations among the polysynaptically activated cells. It is proposed that the asymmetry of distribution seen among the first-order cells reflects the asymmetry seen subcortically in neurones that show orientation biases. It may be that the cortex elaborates a more uniform representation of orientations only at the higher ordinal levels.