Atomic displacement parameters for Ni(ND3)4(NO2)2 from 9 K X-ray and 13 K time-of-flight neutron diffraction data

1996 ◽  
Vol 52 (6) ◽  
pp. 923-931 ◽  
Author(s):  
B. B. Iversen ◽  
F. K. Larsen ◽  
B. N. Figgis ◽  
P. A. Reynolds ◽  
A. J. Schultz
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Data ◽  
Structural Information ◽  
Structural Parameters ◽  
Structure Refinement ◽  
Time Of Flight ◽  
Thermal Parameters ◽  
Neutron Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray

Structural parameters derived from 9 1) K X-ray diffraction data and 13 (1) K time-of-flight neutron diffraction data on perdeuterated tetraamminedinitronickel(II), Ni(ND3)4(NO2)2, are compared. It is shown that excellent agreement can be obtained for both positional and thermal parameters derived separately from the two experiments, provided that great care is taken in all steps of the process, including data collection, data reduction, and nuclear and electronic structure refinement. The mean difference in the thermal parameters, <|ΔUij |>, is as low as 0.00034 Å2 and <(ΔUij/σ)2>1/2 = 1.92, showing that, even without any form of scaling between the parameters, the same values can be obtained. This, compared with other such studies, indicates that time-of-flight neutron diffraction data can give structural information of a quality comparable to monochromatic neutron diffraction. The excellent correspondence between the thermal parameters derived separately from X-ray and neutron diffraction data gives confidence in the deconvolution of the thermal motion from the X-ray diffraction data, which is necessary for any study of a static electron density distribution.

The structure of oxide glasses studied by high-energy x-ray diffraction

2020 ◽  
Vol 61 (6) ◽  
pp. 233-238
Author(s):  
S. Kohara ◽  
◽  
N. Umesaki ◽  
H. Ohno ◽  
K. Suzuya ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Structural Information ◽  
Structural Models ◽  
High Energy ◽  
Reverse Monte Carlo ◽  
Oxide Glasses ◽  
Neutron Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Approaches To Study

The use of high‑energy x‑ray diffraction techniques with the latest generation synchrotron sources has created new approaches to study quantitatively the structure of noncrystalline materials. Recently, this technique has been combined with neutron diffraction at pulsed source to provide more detailed and reliable structural information not previously available. This article reviews and summarises recent results obtained from the high energy x‑ray diffraction on several oxide glasses, SiO2, B2O3 and PbSiO3, using bending magnet beamlines at SPring‑8. In particular, it addresses the structural models of the oxide glasses obtained by the reverse Monte Carlo (RMC) modelling technique using both the high energy x‑ray and neutron diffraction data.

scholarly journals Glycyl-L-alanine: a multi-temperature neutron study

2014 ◽  
Vol 70 (10) ◽  
pp. 949-952 ◽  
Author(s):  
Silvia C. Capelli ◽  
Hans-Beat Bürgi ◽  
Sax A. Mason ◽  
Dylan Jayatilaka
Keyword(s):  
Hydrogen Bonding ◽  
Neutron Diffraction ◽  
Diffraction Data ◽  
Neutron Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydrogen Bonding Interactions ◽  
Anisotropic Displacement Parameters

Neutron diffraction data have been collected at 12, 50, 150 and 295 K for the dipeptide glycyl-L-alanine, C5H10N2O3, in order to obtain accurate positional and anisotropic displacement parameters for the H atoms. The values of these parameters serve as a benchmark for assessing the equivalent parameters obtained from a so-called Hirshfeld-atom refinement of X-ray diffraction data described elsewhere [Capelliet al.(2014).IUCrJ,1, 361–379]. The flexibility of the glycyl-L-alanine molecule in the solid and the hydrogen-bonding interactions as a function of temperature are also considered.

Rietveld refinement of LaB6: data from µXRD

2005 ◽  
Vol 38 (5) ◽  
pp. 757-759 ◽  
Author(s):  
Guangrong Ning ◽  
Roberta L. Flemming
Keyword(s):  
Rietveld Refinement ◽  
Diffraction Data ◽  
Structural Information ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Quality Data ◽  
X Ray Diffraction ◽  
Diffraction Profile ◽  
Standard Material ◽  
X Ray

The Rietveld method of crystal structure refinement was an important breakthrough, allowing crystal structural information to be obtained from powder diffraction data. One remaining challenge is to collect Rietveld-quality data for polycrystalline mineralsin situ, using laboratory-based micro X-ray diffraction (µXRD) techniques. Here a new data collection method is presented, called `multiframes', which produces high-quality data, suitable for Rietveld refinement, using the Bruker D8 DISCOVER micro X-ray diffractometer. 91 frames of two-dimensional X-ray diffraction data were collected for powdered NIST SRM 660 LaB6standard material, using a general area-detector diffraction system (GADDS), at intervals of 0.8° 2θ. For each frame, only the central 1° 2θ was integrated and merged to produce a diffraction profile from 17 to 90° 2θ. Rietveld refinement of this data usingTOPAS2gave a unit-cell parameter (ao) and atomic position of boron (x) for LaB6of 4.1549 (1) Å and 0.1991 (9), respectively (Rwp= 4.26,RBragg= 3.21). The corresponding La—B bond length was calculated to be 3.0522 Å. These parameters are in good agreement with the literature values for LaB6. These encouraging results suggest that Rietveld-quality micro X-ray diffraction data can be collected from the Bruker D8 DISCOVER diffractometer, provided that the GADDS detector is stepped in small increments, for each frame only the central 1° 2θ is integrated at constant arc length, and counting time is sufficient to yield adequate intensity (∼10 000 counts).

TAAM: a reliable and user friendly tool for hydrogen-atom location using routine X-ray diffraction data

2020 ◽  
Vol 76 (3) ◽  
pp. 296-306 ◽  
Author(s):  
Kunal Kumar Jha ◽  
Barbara Gruza ◽  
Prashant Kumar ◽  
Michal Leszek Chodkiewicz ◽  
Paulina Maria Dominiak
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Data ◽  
Structure Refinement ◽  
X Rays ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Bond Lengths ◽  
Atom Model ◽  
User Friendly

Hydrogen is present in almost all of the molecules in living things. It is very reactive and forms bonds with most of the elements, terminating their valences and enhancing their chemistry. X-ray diffraction is the most common method for structure determination. It depends on scattering of X-rays from electron density, which means the single electron of hydrogen is difficult to detect. Generally, neutron diffraction data are used to determine the accurate position of hydrogen atoms. However, the requirement for good quality single crystals, costly maintenance and the limited number of neutron diffraction facilities means that these kind of results are rarely available. Here it is shown that the use of Transferable Aspherical Atom Model (TAAM) instead of Independent Atom Model (IAM) in routine structure refinement with X-ray data is another possible solution which largely improves the precision and accuracy of X—H bond lengths and makes them comparable to averaged neutron bond lengths. TAAM, built from a pseudoatom databank, was used to determine the X—H bond lengths on 75 data sets for organic molecule crystals. TAAM parametrizations available in the modified University of Buffalo Databank (UBDB) of pseudoatoms applied through the DiSCaMB software library were used. The averaged bond lengths determined by TAAM refinements with X-ray diffraction data of atomic resolution (d min ≤ 0.83 Å) showed very good agreement with neutron data, mostly within one single sample standard deviation, much like Hirshfeld atom refinement (HAR). Atomic displacements for both hydrogen and non-hydrogen atoms obtained from the refinements systematically differed from IAM results. Overall TAAM gave better fits to experimental data of standard resolution compared to IAM. The research was accompanied with development of software aimed at providing user-friendly tools to use aspherical atom models in refinement of organic molecules at speeds comparable to routine refinements based on spherical atom model.

scholarly journals A Neutron and X-ray Diffraction Study of the Structure of Nd Phosphate Glasses

2001 ◽  
Vol 56 (3-4) ◽  
pp. 237-243 ◽  
Author(s):  
Uwe Hoppe ◽  
Heike Ebendorff-Heidepriem ◽  
Jörg Neuefeind ◽  
Daniel T. Bowron
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
Coordination Number ◽  
Diffraction Data ◽  
Phosphate Glasses ◽  
Neutron Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxygen Atoms

Abstract Diffraction experiments were performed on two (Nd2O3)x(P2O5)1- x glasses for studying the en­ vironmental order of the Nd3+ cations. In case of the metaphosphate glass (x = 0.25) a combination of X-ray and neutron diffraction data was used to separate the Nd-O and O-O first neighbor peaks. An Nd-O coordination number of 6.6±0.3 and a mean Nd-O distance of (0.239±0.001) nm were determined. In the ultraphosphate glass studied (x = 0.20) these values increase to 6.9±0.3 and (0.240±0.001) nm where the Nd-0 coordination number is equal to the number of terminal oxygen atoms (OT) which are available for coordination of each Nd3+ cation. This indicates the formation of NdOn polyhedra not sharing any O atom where also all OT's are in N d-OT-P positions. In the metaphosphate glass the NdOn polyhedra have to share some OT sites.

scholarly journals The incommensurately modulated structures of low-temperature labradorite feldspars: a single-crystal X-ray and neutron diffraction study

2020 ◽  
Vol 76 (1) ◽  
pp. 93-107
Author(s):  
Shiyun Jin ◽  
Huifang Xu ◽  
Xiaoping Wang ◽  
Ryan Jacobs ◽  
Dane Morgan
Keyword(s):  
Low Temperature ◽  
Neutron Diffraction ◽  
Single Crystal ◽  
Diffraction Data ◽  
Neutron Diffraction Study ◽  
Neutron Diffraction Data ◽  
X Ray Diffraction ◽  
Subsolidus Phase ◽  
X Ray ◽  
Modulated Structures

Labradorite feldspars of the plagioclase solid solution series have been known for their complicated subsolidus phase relations and enigmatic incommensurately modulated structures. Characterized by the irrationally indexed e-reflections in the diffraction pattern, e-labradorite shows the largest variation in the incommensurate ordering states among the e-plagioclase structures. The strongly ordered low-temperature e-labradorite is one of the last missing pieces of the e-plagioclase puzzle. Nine plutonic and metamorphic labradorite feldspar samples from Canada, Ukraine, Minnesota (USA), Tanzania and Greenland with compositions ranging from An52.5 to An68 were studied with single-crystal X-ray diffraction. Two crystals from Labrador, Canada, and Duluth, MN, USA, with wide enough twin lamellae were analyzed with single-crystal neutron diffraction. The incommensurately modulated structures of e-plagioclase are refined for the first time with neutron diffraction data, which confirmed that the T—O distance modulation in the low-temperature e-plagioclase results from the Al–Si ordering in the framework. Detailed configurations of the M site are also observed in the structures refined from neutron diffraction data, which were not possible to see with X-ray diffraction data. The relation between the q-vectors and the mole% An composition is revealed for the entire compositional range of e-plagioclase, from An25 to An75. The previously proposed two-trend relation depending on the cooling rate and phase transition path is confirmed. A new classification of e-plagioclase (e α, e β and e γ) is proposed based on the q-vector of the structure, which makes it an independent character from the presence/absence of density modulation. New parameters are proposed to quantify the ordering states of these complicated aperiodic structures of e-plagioclases, such as the difference between 〈T1o—O〉 and 〈T1m—O〉 at phase t = 0.2 or the normalized intensity of the (071\bar 1) reflection.

Accurate atomic displacement parameters from time-of-flight neutron-diffraction data at TOPAZ

2014 ◽  
Vol 70 (6) ◽  
pp. 679-681 ◽  
Author(s):  
Mads R. V. Jørgensen ◽  
Venkatesha R. Hathwar ◽  
Mattia Sist ◽  
Xiaoping Wang ◽  
Christina M. Hoffmann ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Excellent Agreement ◽  
Diffraction Data ◽  
Time Of Flight ◽  
Atomic Displacement ◽  
Neutron Diffraction Data ◽  
High Quality ◽  
X Ray ◽  
Atomic Displacement Parameters

Accurate atomic displacement parameters (ADPs) are a good indication of high-quality diffraction data. Results from the newly commissioned time-of-flight Laue diffractometer TOPAZ at the SNS are presented. Excellent agreement is found between ADPs derived independently from the neutron and X-ray data emphasizing the high quality of the data from the time-of-flight Laue diffractometer.

Solution of heavy atom structures from powder diffraction data using direct methods. A review of structures solved at Aarhus University

2004 ◽  
Vol 19 (4) ◽  
pp. 362-366
Author(s):  
Axel Nørlund Christensen
Keyword(s):  
Neutron Diffraction ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Inorganic Compounds ◽  
Heavy Atom ◽  
Direct Methods ◽  
Neutron Diffraction Data ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray

Heavy atoms dominate the X-ray scattering from many inorganic compounds like oxides and oxalates, and often only partial structures of these compounds can be obtained by X-ray powder diffraction data. Combining information from X-ray and neutron diffraction data is an advantage. Scattering contributions from the atoms are more evenly distributed in neutron diffraction data than in X-ray diffraction data. Neutron diffraction data can then be used to complete a structure partially solved with data from an X-ray diffraction pattern. Examples of heavy atom structures solved in the time period 1983–2004 using direct methods outlined above are presented.

Accurate molecular structures of chlorothiazide and hydrochlorothiazide by joint refinement against powder neutron and X-ray diffraction data

2008 ◽  
Vol 64 (1) ◽  
pp. 101-107 ◽  
Author(s):  
Charlotte K. Leech ◽  
Francesca P. A. Fabbiani ◽  
Kenneth Shankland ◽  
William I. F. David ◽  
Richard M. Ibberson
Keyword(s):  
Neutron Diffraction ◽  
Rietveld Refinement ◽  
Diffraction Data ◽  
Organic Materials ◽  
Structural Information ◽  
Crystalline Form ◽  
Molecular Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Powder Neutron Diffraction

The compounds chlorothiazide and hydrochlorothiazide (crystalline form II) have been studied in their fully hydrogenous forms by powder neutron diffraction on the GEM diffractometer. The results of joint Rietveld refinement of the structures against multi-bank neutron and single-bank X-ray powder data are reported and show that accurate and precise structural information can be obtained from polycrystalline molecular organic materials by this route.

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