Powder and single crystal diffraction are analytical methods that have developed into widely used tools for material analysis on molecular and atomic level.Dependent on the sample symmetry, the material to be investigated and the question to answer, X-ray diffraction and increasingly also neutron diffraction are the investigative tools of choice due to their complementary sensitivity to heavy and light elements.Data collection with area detectors is more and more automated.Bragg diffraction intensities are collected highly efficiently and data reduction is streamlined.For single crystal structure analysis, raw diffraction intensities are reduced to an extracted structure factor amplitude for each measured Bragg reflection, and the reduced data set represents the composition and symmetry arrangement of the sample.The measured Bragg intensities are raw intensities and need to be corrected for sample absorption due to chemical composition and size, the experimental setup that might add extra scattering, for example glue used to secure the sample, or the detectors that might have variations in detection sensitivity and electronic noise.Those are just a few examples for sample and instrument specific corrections.Other corrections that are dependent on the radiation (X-rays or neutrons) and on monochromatic or polychromatic incident beams are Lorentz and polarization corrections, scaling and normalization.Being aware of the various corrections and when they are applied in the data reduction workflow can help to solve issues that surface during data analysis.Understanding the effects of various corrections are even more important, when relatively weak superlattice intensities or diffuse scattering are studied.This contribution aims to shed light on which corrections are applied to diffraction data, at which step of data reduction they are applied and they might impact the structure factor amplitudes and data analysis.

Recent development in detector technology and source power at x-ray and neutron facilities have leveraged the study of the dynamic response of materials under external stimuli using time-resolved diffraction.Such experiments traditionally use hardware solutions to sort data into their respective histogram bins.We have shown a significant advantage of event-based data acquisition over hardware histogramming by enabling postprocessing utilizing a software solution [1].This approach is made even more powerful for neutron TOF (time-of-flight) Laue diffraction.In addition to volumetric mapping in 3 dimensions, from detector (x,y) positions to wavelength-resolved 3D volume in (x, y, λ) along the neutron TOF direction, we can correlate measured diffraction data with metadata characterizing the applied stimuli (temperature, electric field, etc.) and material response.In this talk, we will present a time-filter approach that leverages the power of event-based diffraction collection on TOPAZ to reduce stroboscopic data representing subsets of the responses to a single cycle of the applied stimulus [1], effectively expanding the measured data beyond three dimensions.We will demonstrate this approach by studying the mechanism that facilitates polarization reorientation in KH2PO4 (KDP) in an alternating applied field using neutron diffraction.Neutron event data collected from a hydrogenated KDP single crystal sample were used to determine how the crystal structure evolves in response to the applied electric fields [2].Field-dependent diffraction data provide evidence that the reorientation of the macroscopic polarization is associated with a subtle change in displacement in the atomic positions through cooperative hydrogen bonding interactions, indicating that polarization reversal is more complex than a simple inversion of the dipoles.

The mechanism that facilitates polarization reorientation in KH2PO4 (KDP) was investigated using operando single-crystal neutron diffraction. Diffraction data were measured from a KDP single crystal during the application of alternating electric fields and were then binned into 40 increments to enable field-dependent single-crystal structure refinements. The field-dependent structures are compared with an as-grown crystal to determine how the lattice and atomic sites evolve in response to the applied electric fields. These analyses provide evidence that the reorientation of the macroscopic polarization is facilitated through a cooperative change in hydrogen bonding, which results in the reversal of the spontaneous dipole. In addition, a decrease in secondary extinction near the coercive field indicates that the inversion of the macroscopic polarization is achieved through the nucleation and subsequent growth of new domains.

Time-resolved diffraction has become a vital tool for probing dynamic responses to an applied stimulus. Such experiments traditionally use hardware solutions to histogram measured data into their respective bin. We will show that a major advantage of event-based data acquisition, which time-stamps measured diffraction data with 100 ns accuracy, is much preferred over hardware histogramming of the data by enabling postprocessing for advanced custom binning using a software solution. This approach is made even more powerful by coupling measured diffraction data with metadata about the applied stimuli and material response. In this work, we present a time-filter approach that leverages the power of event-based diffraction collection to reduce stroboscopic data measured over many hours into equally weighted segments that represent subsets of the response to a single cycle of the applied stimulus. We demonstrate this approach by observing ferroelectric/ferroelastic domain wall motion during electric field cycling of BaTiO3. The developed approach can readily be expanded to investigate other dynamic phenomena using complex sample environments.

The structural phase transition accompanied by a Jahn–Teller switch has been studied over a range of H/D ratios in (NH4)2[Cu(H2O)6](SO4)2 (ACTS). In particular, single-crystal neutron diffraction investigations of crystals with deuteration in the range 50 to 82% are shown to be consistent with previous electron paramagnetic resonance (EPR) experiments exhibiting a phase boundary at 50% deuteration under ambient pressure. Polycrystalline samples show that the two phases can co-exist. In addition, single-crystal neutron and polycrystalline X-ray diffraction pressure experiments show a shift to lower pressure at 60% deuteration versus previous measurements at 100% deuteration.

We report on the intriguing evolution of the dynamical spin correlations of the frustrated spinel ZnMn2O4. Inelastic neutron scattering and magnetization studies reveal that the dynamical correlations at high temperatures are 1D. At lower temperature, these dynamical correlations become 2D. Surprisingly, the dynamical correlations condense into a quasi 2D Ising-like ordered state, making this a rare observation of two dimensional order on the spinel lattice. Remarkably, 3D ordering is not observed down to temperatures as low as 300 mK. This unprecedented dimensional crossover stems from frustrated exchange couplings due to the huge Jahn-Teller distortions around Mn3+ ions on the spinel lattice.

Hydrogen bonds profoundly influence the architecture and activity of biological macromolecules. Deep appreciation of hydrogen bond contributions to biomolecular function thus requires a detailed understanding of hydrogen bond structure and energetics and the relationship between these properties. Hydrogen bond formation energies (ΔGf) are enormously more favorable in aprotic solvents than in water, and two classes of contributing factors have been proposed to explain this energetic difference, focusing respectively on the isolated and hydrogen-bonded species: (I) water stabilizes the dissociated donor and acceptor groups much better than aprotic solvents, thereby reducing the driving force for hydrogen bond formation; and (II) water lengthens hydrogen bonds compared to aprotic environments, thereby decreasing the potential energy within the hydrogen bond. Each model has been proposed to provide a dominant contribution to ΔGf, but incisive tests that distinguish the importance of these contributions are lacking. Here we directly test the structural basis of model II. Neutron crystallography, NMR spectroscopy, and quantum mechanical calculations demonstrate that O-H···O hydrogen bonds in crystals, chloroform, acetone, and water have nearly identical lengths and very similar potential energy surfaces despite ΔGf differences >8 kcal/mol across these solvents. These results rule out a substantial contribution from solvent-dependent differences in hydrogen bond structure and potential energy after association (model II) and thus support the conclusion that differences in hydrogen bond ΔGf are predominantly determined by solvent interactions with the dissociated groups (model I). These findings advance our understanding of universal hydrogen-bonding interactions and have important implications for biology and engineering.

The intensity of single-crystal Bragg peaks obtained by mapping neutron time-of-flight event data into reciprocal space and integrating in various ways is compared. These methods include spherical integration with a fixed radius, ellipsoid fitting and integration of the peak intensity, and one-dimensional peak profile fitting. In comparison to intensities obtained by integrating in real detector histogram space, the data integrated in reciprocal space result in better agreement factors and more accurate atomic parameters. Furthermore, structure refinement using integrated intensities from one-dimensional profile fitting is demonstrated to be more accurate than simple peak-minus-background integration.

Yb3Ga7Ge3 and YbGa4Ge2 were obtained from reactions of Yb and Ge in excess liquid gallium. The crystal structure of Yb3Ga7Ge3 was refined using X-ray and neutron diffraction data on selected single crystals. Yb3Ga7Ge3 crystallizes in the monoclinic space group C2/c with lattice constants a=12.2261(20)Å, b=10.7447(20) Å, c=8.4754(17)Å and β=110.288(30)° (neutron diffraction data). The crystal structure of Yb3Ga7Ge3 is an intergrowth of planar layers of YbGaxGey and puckered layers of (Ge)n. YbGa4Ge2 crystallizes in a modified PuGa6 structure type in the tetragonal polar space group I4cm with lattice constants a=b=5.9874(6)Å and c=15.1178(19)Å. The structure of YbGa4Ge2 is an intergrowth of puckered Ga layers and puckered GaxGey layers with Yb atoms residing within the channels formed by the connection of the two layers. Physical properties, resistivity (ρ), magnetic susceptibility (χ) and specific heat (C) were measured for Yb3Ga7Ge3. No magnetic ordering was observed. It was found that at low temperatures, ρ varied as T2 and C∝T, indicating Fermi-liquid regime in Yb3Ga7Ge3 at low temperatures.

Terminal oxo complexes of the late transition metals Pt, Pd, and Au have been reported by us in Science and Journal of the American Chemical Society. Despite thoroughness in characterizing these complexes (multiple independent structural methods and up to 17 analytical methods in one case), we have continued to study these structures. Initial work on these systems was motivated by structural data from X-ray crystallography and neutron diffraction and (17)O and (31)P NMR signatures which all indicated differences from all previously published compounds. With significant new data, we now revisit these studies. New X-ray crystal structures of previously reported complexes K(14)[P(2)W(19)O(69)(OH(2))] and "K(10)Na(3)[Pd(IV)(O)(OH)WO(OH(2))(PW(9)O(34))(2)]" and a closer examination of these structures are provided. Also presented are the (17)O NMR spectrum of an (17)O-enriched sample of [PW(11)O(39)](7-) and a careful combined (31)P NMR-titration study of the previously reported "K(7)H(2)[Au(O)(OH(2))P(2)W(20)O(70)(OH(2))(2)]." These and considerable other data collectively indicate that previously assigned terminal Pt-oxo and Au-oxo complexes are in fact cocrystals of the all-tungsten structural analogues with noble metal cations, while the Pd-oxo complex is a disordered Pd(II)-substituted polyoxometalate. The neutron diffraction data have been re-analyzed, and new refinements are fully consistent with the all-tungsten formulations of the Pt-oxo and Au-oxo polyoxometalate species.

AbstractThe new title compounds are synthesized in excess liquid Ga from mixtures of Yb, Pd, Ga, and Ge in the atomic ratio 3:2:30:6 (alumina crucible in an evacuated silica tube, 1123 K, 48 h).

The structure of the dichloride hexahydrate cube, [Cl(2)(H(2)O)(6)](2-), as a salt with the tris(diisopropylamino)cyclopropenium cation, [C(3)(N(i)Pr(2))(3)](+), has been determined by low-temperature X-ray and neutron-diffraction studies. H atoms not involved in O-H···Cl bonding are disordered over two 0.5 occupancy sites around the O(6) ring. Calculations of the dianionic cube in the gas phase show remarkably good agreement with the solid-state structures with the exception of short O-H bond distances around the O(6) ring that suggests the involvement of a dynamic process. The cluster was also characterised by single-crystal infrared spectroscopy, and vibrational wavenumbers were found to be in good agreement with hydrogen bonding distances. Dibromide and difluoride hexahydrates were also studied theoretically, and O···O distances were found to decrease in the order difluoride > dichloride > dibromide > (H(2)O)(6) and as O···O···O angles increased towards an almost planar ring in (H(2)O)(6). NMR spectra of a chloroform solution of the hydrated salt at -25 °C is consistent with cluster formation.

Microsymposia C154in the range between 15 and 250°C reveals the occurrence of at least two partially dehydrated phases.From the evaluation of the collected patterns it can be concluded that the principal crystallographic differences between these two materials and the kanemite structure are due to a pronounced decrease of the lattice parameter perpendicular to the silicate layers (direction [010]).An ab-initio structure determination by simulated annealing of the first dehydration product of kanemite with nominal composition NaSi 2 O 4 (OH)*H 2 O was successful.Whereas the silicate layers of the kanemite structure are retained almost unmodified, pronounced changes can be observed in the interlayer sheet containing the Na cations.The previously unknown phase adopts space group Pbcn as well.Lattice parameters at ambient conditions are as follows: a=4.

We studied the properties of the antiferromagnetic (AFM) UNi0.5Sb2 (TN \approx 161 K) compound in Sb-flux grown single crystals by means of measurements of neutron diffraction, magnetic susceptibility ({\chi}), specific heat (Cp), thermopower (S), thermal conductivity ({\kappa}), linear thermal expansion ({\Delta}L/L), and electrical resistivity ({\rho}) under hydrostatic pressures (P) up to 22 kbar. The neutron diffraction measurements revealed that the compound crystallizes in the tetragonal P42/nmc structure, and the value of the U-moments yielded by the histograms at 25 K is \approx 1.85 \pm 0.12 {\mu}B/U-ion. In addition to the features in the bulk properties observed at TN, two other hysteretic features centered near 40 and 85 K were observed in the measurements of {\chi}, S, {\rho}, and {\Delta}L/L. Hydrostatic pressure was found to raise TN at the rate of \approx 0.76 K/kbar, while suppressing the two low temperature features. These features are discussed in the context of Fermi surface and hybridization effects.