Unit-cell refinement from powder diffraction scans

Pawley, G. S.

doi:10.1107/s0021889881009618

Cited by 1,859 publications

(1,466 citation statements)

References 5 publications

(9 reference statements)

Supporting

Mentioning

1,428

Contrasting

Unclassified

Order By: Relevance

“…The diffraction pattern was indexed using DICVOL91 44 to a monoclinic cell [F(18) = 71.0, M(18) = 19.8] and space group P2 1 /n was assigned from volume considerations and a statistical consideration of the systematic absences. The data set was background subtracted and truncated to d = 2.795 Å (2θ = 17.00°), for Pawley refinement 45 and the structure was solved ab initio using the simulated annealing (SA) global optimization procedure implemented in the DASH computer program 46,47 . The SA structure solution involved the optimization of four independent fragments in the asymmetric unit (one Cu atom, two Cl atom and one pyimH ligand), totalling 16 degrees of freedom.…”

Section: Mmol)mentioning

confidence: 99%

Tuning the magneto-structural properties of non-porous coordination polymers by HCl chemisorption

et al. 2012

View full text Add to dashboard Cite

Responsive materials for which physical or chemical properties can be tuned by applying an external stimulus are attracting considerable interest in view of their potential applications as chemical switches or molecular sensors. A potential source of such materials is metalorganic frameworks. These porous coordination polymers permit the physisorption of guest molecules that can provoke subtle changes in their porous structure, thus affecting their physical properties. Here we show that the chemisorption of gaseous HCl molecules by a nonporous one-dimensional coordination polymer instigates drastic modifications in the magnetic properties of the material. These changes result from profound structural changes, involving cleavage and formation of covalent bonds, but with no disruption of crystallinity.

show abstract

Section: Mmol)mentioning

confidence: 99%

Tuning the magneto-structural properties of non-porous coordination polymers by HCl chemisorption

et al. 2012

View full text Add to dashboard Cite

show abstract

“…Powder diffraction patterns were acquired at 25 °C using a Bruker (Bruker AXS, Inc., Madison, WI, USA) General Area Detector Diffraction System (GADDS) equipped with a helium tunnel to reduce air scatter. The program Diffrac plus TOPAS (Bruker AXS GMBH, Karlsruhe, Germany) was used for line shape fitting to the trigonal and orthorhombic unit cell parameters using the Pawley method 32 . Additional experiment details are given in the supporting information.…”

Section: B X-ray Diffractionmentioning

confidence: 99%

Crystal Polymorphism of Protein GB1 Examined by Solid-State NMR Spectroscopy and X-ray Diffraction

et al. 2007

View full text Add to dashboard Cite

The study of micro-or nanocrystalline proteins by magic-angle spinning (MAS) solid-state NMR (SSNMR) gives atomic-resolution insight into structure in cases when single crystals cannot be obtained for diffraction studies. Subtle differences in the local chemical environment around the protein, including the characteristics of the co-solvent and the buffer, determine whether a protein will form single crystals. The impact of these small changes in formulation is also evident in the SSNMR spectra, but leads only to correspondingly subtle changes in the spectra. Here we demonstrate that several formulations of GB1 microcrystals yield very high-quality SSNMR spectra, although only a subset of conditions enable growth of single crystals. We have characterized these polymorphs by X-ray powder diffraction and assigned the SSNMR spectra. Assignments of the 13 C and 15 N SSNMR chemical shifts confirm that the backbone structure is conserved, indicative of a common protein fold, but sidechain chemical shifts are changed on the surface of the protein, in a manner dependent upon crystal packing and electrostatic interactions with salt in the mother liquor. Our results demonstrate the ability of SSNMR to reveal minor structural differences among crystal polymorphs. This ability has potential practical utility for studying formulation chemistry of industrial and therapeutic proteins, as well as for deriving fundamental insights into the phenomenon of single crystal growth.

show abstract

“…This could be a LeBail or Pawley fit if lattice parameters are of interest, or Rietveld refinement if structural information is also desired. 94,95 Rietveld refinement is the preferred approach to confirm phase purity, as it considers peak intensities as well as locations, which will prove impossible to fit well should there exist multiple phases with overlapped peaks. The Rietveld approach will also naturally provide a quantitative measure of the various phases present in a sample in the case of secondary phases.…”

Section: Analysis Of Powdersmentioning

confidence: 99%

Perovskite-Inspired Photovoltaic Materials: Toward Best Practices in Materials Characterization and Calculations

et al. 2017

View full text Add to dashboard Cite

ABSTRACT:Recently, there has been an explosive growth in research based on hybrid lead-halide perovskites for photovoltaics owing to rapid improvements in efficiency. The advent of these materials for solar applications has led to widespread interest in understanding the key enabling properties of these materials. This has resulted in renewed interest in related compounds and a search for materials that may replicate the defect-tolerant properties and long lifetimes of the hybrid lead-halide perovskites. Given the rapid pace of development of the field, the rises in efficiencies of these systems have outpaced the more basic understanding of these materials. Measuring or calculating the basic properties, such as crystal/electronic structure and composition, can be challenging because some of these materials have anisotropic structures, and/or are composed of both heavy metal cations and volatile, mobile, light elements. Some consequences are beam damage during characterization, composition change under vacuum, or compound effects, such as the alteration of the electronic structure through the influence of the substrate. These effects make it challenging to understand the basic properties integral to optoelectronic operation. Compounding these difficulties is the rapid pace with which the field progresses. This has created an ongoing need to continually evaluate best practices with respect to characterization and calculations, as well as to identify inconsistencies in reported values to determine if those inconsistencies are rooted in characterization methodology or materials synthesis. This article describes the difficulties in characterizing hybrid lead-halide perovskites and new materials, and how these challenges may be overcome. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 challenges discussed. The focus in this article is on crystallography, composition measurements, photoemission spectroscopy and calculations on perovskites and new, related absorbers. We suggest how some of the important artifacts could be avoided and how the reporting for each technique could be streamlined between groups to ensure reproducibility as the field progresses.

show abstract

Unit-cell refinement from powder diffraction scans

Cited by 1,859 publications

References 5 publications

Tuning the magneto-structural properties of non-porous coordination polymers by HCl chemisorption

Tuning the magneto-structural properties of non-porous coordination polymers by HCl chemisorption

Crystal Polymorphism of Protein GB1 Examined by Solid-State NMR Spectroscopy and X-ray Diffraction

Perovskite-Inspired Photovoltaic Materials: Toward Best Practices in Materials Characterization and Calculations

Contact Info

Product

Resources

About