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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Spotlight: efficient automated global optimization in rietveld analysis of diffraction data

Performing reliable Rietveld analysis on tens or hundreds of powder diffraction datasets from parametric or time-resolved experiments often poses a bottleneck in extracting meaningful results from the data. While automated analysis of data has recently been demonstrated, high temperature annealing studies, during which phase transformations occur and lattice parameters may change due to repartitioning of elements, are prime examples where automation by a simple phase identification from a database of room temperature structures or automation by sequential refinements is likely to fail. To enable reliable, efficient, automated Rietveld analysis, we present a Python package named Spotlight , building on established Rietveld packages such as MAUD, GSAS , or GSAS-II , which extends the refinement of best fit parameters to a global optimization using an ensemble of optimizers leveraging hierarchical parallel execution on high-performance computing clusters. Spotlight further enables the efficient design of refinement plans through the iterative automated machine-learning of a surrogate for the refinement on which the global optimizations are performed until results from the surrogate converge to the response surface data. We demonstrate Spotlight with the analysis of uranium molybdenum and Ti–6Al–4V datasets, as well as in two open-source tutorials analyzing aluminium oxide and lead sulphate.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Recent developments targeting new and experienced users in EXPGUI, an open source Rietveld analysis interface.

EXPGUI is an open source interface that supplements the GSAS program package, which together provide a powerful set of tools for structure refinement, especially Rietveld Analysis. The combined GSAS-EXPGUI packages are freely distributed and are ideal for both new and experienced users. The latest EXPGUI version includes many new intuitive features including methods of implementing distance restraints, fixing coordinates, advanced searching and viewing of interatomic distances and angles as well as improved user friendliness and much more.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2023

MILK : a Python scripting interface to MAUD for automation of Rietveld analysis

Modern diffraction experiments ( e.g. in situ parametric studies) present scientists with many diffraction patterns to analyze. Interactive analyses via graphical user interfaces tend to slow down obtaining quantitative results such as lattice parameters and phase fractions. Furthermore, Rietveld refinement strategies ( i.e. the parameter turn-on-off sequences) tend to be instrument specific or even specific to a given dataset, such that selection of strategies can become a bottleneck for efficient data analysis. Managing multi-histogram datasets such as from multi-bank neutron diffractometers or caked 2D synchrotron data presents additional challenges due to the large number of histogram-specific parameters. To overcome these challenges in the Rietveld software Material Analysis Using Diffraction ( MAUD ), the MAUD Interface Language Kit ( MILK ) is developed along with an updated text batch interface for MAUD . The open-source software MILK is computer-platform independent and is packaged as a Python library that interfaces with MAUD . Using MILK , model selection ( e.g. various texture or peak-broadening models), Rietveld parameter manipulation and distributed parallel batch computing can be performed through a high-level Python interface. A high-level interface enables analysis workflows to be easily programmed, shared and applied to large datasets, and external tools to be integrated with MAUD . Through modification to the MAUD batch interface, plot and data exports have been improved. The resulting hierarchical folders from Rietveld refinements with MILK are compatible with Cinema: Debye–Scherrer , a tool for visualizing and inspecting the results of multi-parameter analyses of large quantities of diffraction data. In this manuscript, the combined Python scripting and visualization capability of MILK is demonstrated with a quantitative texture and phase analysis of data collected at the HIPPO neutron diffractometer.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2016

Rietveld analysis using powder diffraction data with anomalous scattering effect obtained by focused beam flat sample method

Focused-beam flat-sample method (FFM) is a new trial for synchrotron powder diffraction method, which is a combination of beam focusing optics, flat shape powder sample and area detectors. The method has advantages for X-ray diffraction experiments applying anomalous scattering effect (anomalous diffraction), because of 1. Absorption correction without approximation, 2. High intensity X-rays of focused incident beams and high signal noise ratio of diffracted X-rays 3. Rapid data collection with area detectors. We applied the FFM to anomalous diffraction experiments and collected synchrotron X-ray powder diffraction data of CoFe{sub 2}O{sub 4} (inverse spinel structure) using X-rays near Fe K absorption edge, which can distinguish Co and Fe by anomalous scattering effect. We conducted Rietveld analyses with the obtained powder diffraction data and successfully determined the distribution of Co and Fe ions in CoFe{sub 2}O{sub 4} crystal structure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

The existence of amorphous phase in Portland cements: Physical factors affecting Rietveld quantitative phase analysis

Rietveld quantitative phase analysis has become a widespread tool for the characterization of Portland cement, both for research and production control purposes. One of the major remaining points of debate is whether Portland cements contain amorphous content or not. This paper presents detailed analyses of the amorphous phase contents in a set of commercial Portland cements, clinker, synthetic alite and limestone by Rietveld refinement of X-ray powder diffraction measurements using both external and internal standard methods. A systematic study showed that the sample preparation and comminution procedure is closely linked to the calculated amorphous contents. Particle size reduction by wet-grinding lowered the calculated amorphous contents to insignificant quantities for all materials studied. No amorphous content was identified in the final analysis of the Portland cements under investigation.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Cation ordering and physicochemical characterization of the quaternary diamond-like semiconductor Ag[subscript 2]CdGeS[subscript 4]

The quaternary diamond-like semiconductor, Ag2CdGeS4, was synthesized via high-temperature solid-state synthesis as well as structurally and physicochemically characterized. Single crystal X-ray diffraction provided a model for Ag2CdGeS4 in the orthorhombic, noncentrosymmetric space group Pna21 with a=13.7415(8) {angstrom}, b=8.0367(5) {angstrom} and c=6.5907(4) {angstrom}, in contrast to a previously published model in Pmn21 from the Rietveld analysis of laboratory X-ray powder diffraction data. The Pna21 space group is supported by the Rietveld analysis of synchrotron X-ray powder diffraction data. Differential thermal analysis suggests that Ag2CdGeS4 exists in two polymorphs. Optical diffuse reflectance UV/vis/NIR spectroscopy indicates that the orange compound is a semiconductor with a band gap of 2.32 eV. Optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and inductively coupled plasma optical emission spectroscopy were used to further characterize the material.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Neutron and X-ray diffraction studies on the high temperature phase of Mn{sub 3}(VO{sub 4}){sub 2}, the new isostructural compound NaMn{sub 4}(VO{sub 4}){sub 3} and their mixed crystals Na{sub x}Mn{sub 4.5-x/2}(VO{sub 4}){sub 3} (0{<=}x{<=}1)

This paper presents a detailed structure analysis (combined Rietveld analysis of X-ray and neutron powder diffraction data as well as quantum mechanical calculations) of the high temperature phase of Mn{sub 3}(VO{sub 4}){sub 2} (space group I4 Macron 2d). Special attention is directed to the analysis of the local coordination around Mn{sup 2+} ions or vacancies within a stella quadrangula configuration of anions. Furthermore, the new compound NaMn{sub 4}(VO{sub 4}){sub 3} is described as well as a range of mixed crystals between NaMn{sub 4}(VO{sub 4}){sub 3} and Mn{sub 3}(VO{sub 4}){sub 2} (described by the formula Na{sub x}Mn{sub 4.5-x/2}(VO{sub 4}){sub 3}, 0{<=}x{<=}1) which were synthesized by a solid state route. All compounds were shown to be isostructural to the high temperature phase Mn{sub 3}(VO{sub 4}){sub 2}. - Graphical abstract: The crystal structure of the new compound NaMn{sub 4}(VO{sub 4}){sub 3}. Highlights: Black-Right-Pointing-Pointer We present neutron and X-ray diffraction studies on high temperature-Mn{sub 3}(VO{sub 4}){sub 2}. Black-Right-Pointing-Pointer Structural details of partly filled stellae quadrangulae positions are discussed. Black-Right-Pointing-Pointer Refined structural parameters and theoretical calculations are compared. Black-Right-Pointing-Pointer We investigate the mixed crystal system Mn{sub 3}(VO{sub 4}){sub 2}-NaMn{sub 4}(VO{sub 4}){sub 3}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Presence of a monoclinic (Pm) phase in the morphotropic phase boundary region of multiferroic (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} solid solution: A Rietveld study

We present here the results of structural studies on multiferroic (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} solid solution using Rietveld analysis on powder x-ray diffraction data in the composition range 0.35 ≤ x ≤ 0.55. The stability region of various crystallographic phases at room temperature for (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} is determined precisely. Structural transformation from pseudo-cubic (x ≤ 0.40) to tetragonal (x ≥ 0.50) phase is observed via phase coexistence region demarcating the morphotropic phase boundary. The morphotropic phase boundary region consists of coexisting tetragonal and monoclinic structures with space group P4mm and Pm, respectively, stable in composition range 0.41 ≤ x ≤ 0.49 as confirmed by Rietveld analysis. The results of Rietveld analysis completely rule out the coexistence of rhombohedral and tetragonal phases in the morphotropic phase boundary region reported by earlier workers. A comparison between the bond lengths for “B-site cations-oxygen anions” obtained after Rietveld refinement, with the bond length calculated using Shannon-Prewitt ionic radii, reveals the ionic nature of B-O (Ni/Ti-O) bonds for the cubic phase and partial covalent character for the other crystallographic phases.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

In situ high-temperature X-ray diffraction study of Sc-doped titanium oxide nanocrystallites

Titanium dioxide is an inexpensive wide-gap highly ionic semiconductor with striking photocatalytic capabilities in several heterogeneous photoredox reactions. A small crystal size is desirable to maximize the surface area, since photocatalytic reactions occur at the surface of a photocatalyst. Presented in this work are the synthesis and microstructural characterization of 4 at.% Sc-doped TiO 2 (4SDT) prepared by water-based co-precipitation. The crystal structure of 4SDT was examined via in situ high-temperature powder X-ray diffraction experiments from 25 to 1200°C. Rietveld analysis revealed single-phase anatase up to 875°C, while at 900°C the anatase-to-rutile phase transformation occurred and at higher temperatures additional reflections of Sc-rich phases (Sc 2 TiO 5 from 975°C and Ti 3 Sc 4 O 12 or Sc 2 O 3 at 1200°C) were observed. Debye function analysis (DFA) was applied to model the total scattering pattern directly in reciprocal space, allowing the reconstruction of Ti vacancies. Both Rietveld and DFA methods were applied to estimate the nanocrystallite size and shape with consistent growth in crystallite size with temperature: an ellipsoid shape with equatorial ~4.7 nm / axial (001) ~6.9 nm at 25°C to equatorial ~27.9 nm / axial (001) ~39.6 nm at 900°C refined by Rietveld analysis, versus a cylinder shape with D a , b = 4.3 nm and size dispersion σ ab = 1.5 nm, L c = 4.9 nm and σ c = 2.3 nm at 25°C to D a , b = 21.4 nm, σ ab = 8.3 nm, L c = 23.9 and σ c = 10.9 nm at 900°C estimated by DFA. The microstructural changes obtained by Rietveld and DFA methods were supported by high-resolution transmission electron microscopy image analysis, as well as by the less direct nitrogen sorption techniques that provide information on the size of non-agglomerated and dense particles. The Ti site-occupancy factor showed a linear increase from 0.6–0.8 at 25°C to unity at 900°C for anatase, and from ~0.7 at 900°C to unity at 1200°C for rutile, via Rietveld analysis and DFA.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Structure of β-AgGaO{sub 2}; ternary I–III–VI{sub 2} oxide semiconductor with a wurtzite-derived structure

The structure of the wurtzite-derived β-AgGaO{sub 2} was refined by Rietveld analysis of high-resolution powder diffraction data obtained using synchrotron X-ray radiation. The space group of the crystal is Pna2{sub 1} with lattice parameters of a{sub 0}=5.56175 Å, b{sub 0}=7.14749 Å, and c{sub 0}=5.46875 Å. The deviation of O–Ag–O and M–O–M bond angles from the regular tetrahedral angle of 109.5° was very large at ∼8° and ∼11°, respectively. The electronic structure of β-AgGaO{sub 2} is discussed based on its structure, and the indirect band gap of β-AgGaO{sub 2} was related to significant tetrahedral distortion. Although β-AgGaO{sub 2} decomposes into metallic silver and Ga{sub 2}O{sub 3} at a high temperature in any atmosphere, β-AgGaO{sub 2} is stable up to 690 °C under an O{sub 2} atmosphere. No direct transformation from the wurtzite-derived phase to a delafossite phase occurs in β-AgGaO{sub 2}. - Graphical abstract: Crystal structure of β-AgGaO{sub 2} was refined by Rietveld analysis. AgO{sub 4} and O(Ag,Ga){sub 4} tetrahedra are significantly distorted from ideal tetrahedron. - Highlights: • Orthorhombic β-AgGaO{sub 2} with a wurtzite-derived β-NaFeO{sub 2} structure was synthesized. • Its structure was refined by Rietveld analysis of high-resolution XRD data. • Silver and oxygen tetrahedra are significantly distorted from an ideal tetrahedron. • The extent of this tetrahedral distortion is related to the band gap nature. • β-AgGaO{sub 2} is a metastable phase but is stable up to 690 °C in an O{sub 2} atmosphere.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Effect of cation distribution on the magnetic and hyperfine behaviour of nanocrystalline Co doped Ni–Zn ferrite (Ni{sub 0.4}Zn{sub 0.4}Co{sub 0.2}Fe{sub 2}O{sub 4})

Highlights: • Cation distribution in tetrahedral and octahedral sites of spinel Ni{sub 0.4}Zn{sub 0.4}Co{sub 0.2}Fe{sub 2}O{sub 4}. • Structural analysis of observed X-ray diffraction pattern using Rietveld method. • Study of hyperfine behaviour using Mössbauer spectroscopy. • Static and dynamic magnetic measurements. • Correlation of cation distributions obtained from Rietveld analysis with the results of magnetic and Mössbauer effect measurements. - Abstract: Nanoparticles of Ni{sub 0.4}Zn{sub 0.4}Co{sub 0.2}Fe{sub 2}O{sub 4} are prepared by a simple co-precipitation method. The as dried sample is heat treated at 400, 500, 600, 700 and 800 °C to obtain different sizes of nanoparticles. The crystallographic phase of the samples is confirmed analyzing observed X-ray diffraction (XRD) by Rietveld method. Hyperfine parameters of the samples are derived from room temperature (RT) Mössbauer spectra of the samples. Magnetic properties of the samples are investigated by static and dynamic hysteresis loops. Different magneto-crystalline parameters are calculated from the variation of magnetization with temperature (M–T curve) under zero field cooled (ZFC) and field cooled (FC) conditions of the as dried sample. The cation distribution estimated from Rietveld analysis are correlated with the results of magnetic and Mössbauer effect measurements. The observed high value of saturation magnetization (72.7 emu/g at RT) of the sample annealed at 800 °C would be interesting for applications in different electromagnetic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Enabling Real-time Scattering Data Analysis with Scalable Optimization [Slides]

Diffraction experiments produce datasets with rich multidimensional physics information such as microstructure, equations of state, crystal structure, elastoplastic properties, and other key inputs to LANL mission-essential multiphysics models. This information is typically extracted through a process called Rietveld refinement, which involves selecting appropriate models of the instrument, crystal structure, and microstructure, identifying suitable starting values, and then fitting often hundreds of model parameters using a sequence of empirical parameter turnon/off sequences within a non-global gradient-based optimization. Extensive user expertise is required to properly setup a refinement, identify appropriate models, and select initial parameter values close to truth, such that the refinement will yield parameter values that are optimally predictive. This is a very tedious manual process performed far after the beamline campaign has ended. As facilities have become capable of generating larger volumes of data, the limitation in throughput due to Rietveld refinement has led to a dramatic increase in unanalyzed data as opposed to an intended increase in new science. In our FY22 TED, we demonstrated an integrated toolset providing near real-time automated Rietveld analysis. If this toolset can be optimized to provide automated Rietveld analysis in real-time, this could alleviate the bottleneck in unanalyzed diffraction data, aid in decision-making during experiments, and increase efficiency of the facility.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2012

Crystal structure and non-stoichiometry of cerium brannerite: Ce{sub 0.975}Ti{sub 2}O{sub 5.95}

The crystal structure of cerium brannerite, Ce{sub 0.975}Ti{sub 2}O{sub 5.95}, was determined from Rietveld analysis of high resolution neutron powder diffraction data (space group C2/m, a=9.8320(1) A, b=3.75287(6) A, c=6.8852(1) A, {beta}=119.230(1) Degree-Sign ). The presence of both cerium and oxygen vacancies was confirmed from Rietveld analysis and defect energy calculations, combined with careful investigation of the phase diagram. Formation of oxygen vacancies at the O1 site, charge compensated by Ce vacancies, relieves considerable Coulombic repulsion and hence structural strain associated with short O1-O1 contacts forming the shared edge of neighbouring TiO{sub 6} polyhedra. Consideration of the bond valence sum of Ce{sup 4+} in Ce{sub 0.975}Ti{sub 2}O{sub 5.95} afforded a revised value of the r{sub 0}=2.098{+-}0.039 A for the reference bond length, based on analysis of 21 crystal structures mined from the ICSD. - Graphical abstract: Neutron diffraction and atomistic defect energy calculations reveal the mechanism of nonstochiometry in cerium brannerite, Ce{sub 0.975}Ti{sub 2}O{sub 5.95}. Highlights: Black-Right-Pointing-Pointer The defect brannerite Ce{sub 0.975}Ti{sub 2}O{sub 5.95} was prepared by solid state synthesis. Black-Right-Pointing-Pointer Neutron diffraction confirmed the presence of Ce vacancies charge compensated by O vacancies. Black-Right-Pointing-Pointer Defect energy calculations show oxygen vacancies relieve structural strain associated with short O-O contact distances.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Enabling phase quantification of anhydrous cements via Raman imaging

The phase composition of Portland cements is typically determined using conventional techniques like X-ray Diffraction (XRD) Rietveld analysis, optical microscopy point counting, and electron microscopy. However, these techniques have several limitations that may affect their accuracy in certain sample-specific scenarios. Here, we report a highly accurate phase quantification of 11 different types of commercial, anhydrous cements using a new and complementary technique: Raman imaging. Specifically, for the 4 principal phases, composition from our extensive data (250,000 Raman spectra per sample, error < 0.71%) and those obtained from XRD Rietveld and supplier data have high coefficients of determination (R{sup 2} > 0.98, mean deviation <2%). Additionally, we also quantify 8 secondary phases present in cement clinkers (gypsum, anhydrite, bassanite, syngenite, dolomite, calcite, quartz, and portlandite) with a high degree of confidence, thereby demonstrating that Raman imaging is a highly versatile tool for anhydrous phase quantification in a broad variety of cements.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Structures and magnetic properties of new fluorite-related quaternary rare earth oxides LnY{sub 2}TaO{sub 7} and LaLn{sub 2}RuO{sub 7} (Ln=rare earths)

New fluorite-related quaternary rare earth oxides LnY{sub 2}TaO{sub 7} (Ln=La–Dy) and LaLn{sub 2}RuO{sub 7} (Ln=Eu–Tb) have been prepared. They crystallize in an orthorhombic superstructure of cubic fluorite with space groups C222{sub 1} and Cmcm, respectively. The results of the Rietveld analysis for LnY{sub 2}TaO{sub 7} (Ln=La–Dy) indicate that there exists no structural ordering of the Ln and Y ions at the eight-coordinate 4b site and the seven-coordinate 8c site, but the larger Ln ions occupy the eight-coordinate 4b site rather than the seven-coordinate 8c site, with increasing the Ln ionic radius. On the other hand, the results of the Rietveld analysis for the X-ray diffraction profiles of LaTb{sub 2}RuO{sub 7} showed that La and Tb atoms are almost situated at the eight-coordinated site (4a site) and seven-coordinated site (8g site), respectively, i.e., cation ordering occurs on the 4a and 8g sites. All compounds LnY{sub 2}TaO{sub 7} (Ln=La–Dy) are paramagnetic down to 1.8 K. On the other hand, LaTb{sub 2}RuO{sub 7} shows an antiferromagnetic transition at 17 K. In addition, another magnetic anomaly has been found at 10 K. Analysis of the magnetic specific heat for LaTb{sub 2}RuO{sub 7} indicates that the magnetic transitions at 10 and 17 K are due to the magnetic ordering of Tb{sup 3+} and Ru{sup 5+} ions, respectively. - Graphical abstract: Two magnetic anomalies have been observed in the temperature dependence of ∂(χT)/∂T for LaTb{sub 2}RuO{sub 7}. It is discussed that the anomalies at 10 and 17 K are due to the magnetic ordering of Tb{sup 3+} and Ru{sup 5+} ions, respectively. - Highlights: • New fluorite-related quaternary rare earth oxides Ln′Ln″{sub 2}MO{sub 7} have been prepared. • All compounds LnY{sub 2}TaO{sub 7} (Ln=La–Dy) are paramagnetic down to 1.8 K. • LaTb{sub 2}RuO{sub 7} shows two magnetic anomalies at 10 and 17 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

An in-situ neutron diffraction study of a multi-phase transformation and twinning-induced plasticity steel during cyclic loading

In-situ neutron diffraction during cyclic tension-compression loading (∼+3.5% to −2.8%) of a 17Mn-3Al-2Si-1Ni-0.06C steel that exhibits concurrent transformation and twinning -induced plasticity effects indicated a significant contribution of intragranular back stresses to the observed Bauschinger effect. Rietveld analysis revealed a higher rate of martensitic transformation during tension compared to compression. Throughout cycling, α′-martensite exhibited the highest phase strains such that it bears an increasing portion of the macroscopic load as its weight fraction evolves. On the other hand, the ε-martensite strain remained compressive as it accommodated most of the internal strains caused by the shape misfit associated with the γ→ε and/or ε→α′ transformations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗