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0000-0003-0776-2692
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Other Physical Sciences | Solid State Chemistry | Chemical Spectroscopy | Condensed Matter Physics | Ceramics | Materials Engineering | Materials Engineering Not Elsewhere Classified | Synchrotrons; Accelerators; Instruments and Techniques | Instruments And Techniques | Condensed Matter Physics—Other
ANZSRC Socio-Economic Objective (SEO)
Inorganic industrial chemicals | Ceramics, glass and industrial mineral products | Ceramics | Other | Energy storage | Expanding Knowledge in the Earth Sciences | Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Physical Sciences | Chemical sciences |
Related Links
Publications
Diffuse scattering as an aid to the understanding of polymorphism in pharmaceuticals
Publisher: Springer Science and Business Media LLC
Date: 10-05-2012
Diffuse scattering and the mechanism for the phase transition in triglycine sulphate
Publisher: Springer Science and Business Media LLC
Date: 31-05-2013
The crystal and magnetic structures of LaCa 2 Fe 3-x M x O 8 (M=Al, Ga, In)
Publisher: Elsevier BV
Date: 12-2012
Diffuse X-ray scattering from benzil, C14H10O2: analysis via automatic refinement of a Monte Carlo model
Publisher: International Union of Crystallography (IUCr)
Date: 2001
DOI: 10.1107/S0108767300013659
Abstract: A recently developed method for fitting a Monte Carlo computer-simulation model to observed single-crystal diffuse X-ray scattering has been used to study the diffuse scattering in benzil, diphenylethanedione, C(6)H(5)-CO-CO-C(6)H(5). A model involving 13 parameters consisting of 11 intermolecular force constants, a single intramolecular torsional force constant and a local Debye-Waller factor was refined to give an agreement factor, R = [summation operator omega(Delta I)(2)/summation operator omega I(obs)(2)](1/2), of 14.5% for 101,324 data points. The model was purely thermal in nature. The analysis has shown that the diffuse lines, which feature so prominently in the observed diffraction patterns, are due to strong longitudinal displacement correlations. These are transmitted from molecule to molecule via a network of contacts involving hydrogen bonding of an O atom on one molecule and the para H atom of the phenyl ring of a neighbouring molecule. The analysis also allowed the determination of a torsional force constant for rotations about the single bonds in the molecule. This is the first diffuse scattering study in which measurement of such internal molecular torsion forces has been attempted.
Local Ordering in Lead-Based Relaxor Ferroelectrics
Publisher: American Chemical Society (ACS)
Date: 04-06-2013
DOI: 10.1021/AR400073W
Abstract: Lead-based ferroelectric materials are both well-studied and widely used and have a wide range of applications from ultrasonics to energy harvesting and beyond. However, the use of Pb-containing materials is environmentally undesirable, due to the toxicity of lead. This is particularly highlighted by the disposal of Pb-based devices when their lifespan is through. Because of this large drawback, chemists have been searching for Pb-free ferroic materials that can replace PZN (PbZn1/3Nb2/3O3), PMN (PbMg1/3Nb2/3O3), PZT (PbZr1-xTixO3), and all their derivatives. Underlying much of materials chemistry is the idea that function arises from structure, so if we can determine the structure of a material, we can understand how its useful properties arise. This understanding can then lead to the tuning of these properties and the development of new materials. However, the question arises: What is meant by structure? Conventionally, structure is determined by X-ray or neutron diffraction, in which the Bragg peak intensities are measured and a unit cell is determined. In many materials, local ordering, order that persists only for few unit cells or nanometers, is important in determining the physical properties. This is very much the case in the relaxor ferroelectrics, an important class of functional oxides. Indeed, disorder, randomness, and short-range order (SRO) are all invoked to help explain many of the key properties. The local order in Pb-based ferroelectrics has been extensively studied, with the most definitive probe being single-crystal diffuse scattering. In this Account, I outline the current debate on the nature of the local order and explore how this information can inform the search for lead-free materials. Local order, as distinct from the overall average order revealed by conventional techniques, relates more closely to the crystal chemistry of the in idual ions and so appears to give a better insight into how the crystal chemistry leads to the ferroelectric properties.
A Process for Modelling Diffuse Scattering from Disordered Molecular Crystals, Illustrated by Application to Monoclinic 9-Chloro-10-methylanthracene
Publisher: Hindawi Limited
Date: 2015
DOI: 10.1155/2015/878463
Abstract: Diffuse scattering from a crystal contains valuable information about the two-body correlations (related to the nanoscale order) in the material. Despite years of development, the detailed analysis of single crystal diffuse scattering (SCDS) has yet to become part of the everyday toolbox of the structural scientist. Recent decades have seen the pair distribution function approach to diffuse scattering (in fact, total scattering) from powders become a relatively routine tool. However, analysing the detailed, complex, and often highly anisotropic three-dimensional distribution of SCDS remains valuable yet rare because there is no routine method for undertaking the analysis. At present, analysis requires significant investment of time to develop specialist expertise, which means that the analysis of diffuse scattering, which has much to offer, is not incorporated thorough studies of many compounds even though it has the potential to be a very useful adjunct to existing techniques. This article endeavours to outline in some detail how the diffuse scattering from a molecular crystal can be modelled relatively quickly and largely using existing software tools. It is hoped this will provide a template for other studies. To enable this, the entire simulation is included as deposited material.
The crystal and magnetic structures of LaCa2Fe3O8 and NdCa2Fe3O8
Publisher: IOP Publishing
Date: 25-02-2009
DOI: 10.1088/0953-8984/21/12/124206
Abstract: The crystal and magnetic structures of LaCa(2)Fe(3)O(8) and NdCa(2)Fe(3)O(8) have been established using a combination of x-ray, neutron and electron diffraction. It was already considered likely that LaCa(2)Fe(3)O(8) and NdCa(2)Fe(3)O(8) were made up of stacked perovskite-like layers of FeO(6) octahedra, with every third layer being replaced by a layer of tetrahedrally coordinated Fe, rather like a variation on the Brownmillerite (Ca(2)Fe(2)O(5)) structure type. We have gone further and determined a likely space group for this Grenier phase and determined the magnetic structure of the compounds at room temperature. The space group is found to be P 2(1)ma (b axis as the long axis), and the crystal structure has been refined, subject to the stacking faulting along the long axis that is apparent in electron diffraction patterns. The magnetic structure of LaCa(2)Fe(3)O(8) is shown to consist of antiferromagnetically ordered Fe(3+) ions on a collinear G-type antiferromagnetic structure, with the magnetic moments most likely (anti)parallel with the c axis, and of magnitude 3.4 ± 0.2μ(B) (3.6 ± 0.2μ(B) for NdCa(2)Fe(3)O(8)). The result is reasonable given the magnetic structures of the end members of the La(1-x)Ca(x)FeO(3) series, LaFeO(3) (x = 0) and Ca(2)Fe(2)O(5) (x = 1).
Rapid Microwave Synthesis and Structural Phase Diagram of LnxY1−xMnO3
Publisher: Walter de Gruyter GmbH
Date: 02-06-2014
Abstract: YMnO 3 is one of the primary ex les of a multiferroic ceramic. We present a novel solid-state microwave sintering method for making high-purity ceramic s les of YMnO 3 and related compounds in a few hours. This leads to determination of the structural phase diagram for the formation of single-phase, hexagonal s les when doping lanthanides into YMnO 3 . It is found that the solidstate microwave synthesis allows manufacture of high-quality s les in hours rather than days. The resulting phase diagram accords well with results from the literature, and from calculations based on the Goldschmidt tolerance factor for the stability of perovskite structures, suggesting that the transformation from hexagonal to perovskite with doping is driven essentially by ion sizes. Some results concerning the microwave synthesis of BaLnInO 4 compounds, where Ln is a lanthanide, are noted. Microwave sintering of BaNdInO 4 yields single-phase s les where conventional sintering does not.
A combined diffraction (XRD, electron and neutron) and electrical study of Na3MoO3F3
Publisher: Elsevier BV
Date: 09-2003
Quasielastic scattering in PrAl3
Publisher: Elsevier BV
Date: 12-1997
Measuring Single-Crystal Diffuse Neutron Scattering on the Wombat High-Intensity Powder Diffractometer
Publisher: Springer Science and Business Media LLC
Date: 11-06-2012
Approaches to Modeling Diffuse Scattering from Molecular Crystals: Para-Terphenyl (C18H14)
Publisher: Springer Science and Business Media LLC
Date: 23-06-2010
Structure and magnetism in Ho1−xSrxCoO3−δ
Publisher: Elsevier BV
Date: 2005
Temperature Dependence of Diffuse Scattering in PZN
Publisher: Springer Science and Business Media LLC
Date: 12-08-2012
Total scattering and pair distribution function analysis in modelling disorder in PZN (PbZn1/3Nb2/3O3)
Publisher: International Union of Crystallography (IUCr)
Date: 2016
DOI: 10.1107/S2052252515018722
Abstract: The ability of the pair distribution function (PDF) analysis of total scattering (TS) from a powder to determine the local ordering in ferroelectric PZN (PbZn 1/3 Nb 2/3 O 3 ) has been explored by comparison with a model established using single-crystal diffuse scattering (SCDS). While X-ray PDF analysis is discussed, the focus is on neutron diffraction results because of the greater extent of the data and the sensitivity of the neutron to oxygen atoms, the behaviour of which is important in PZN. The PDF was shown to be sensitive to many effects not apparent in the average crystal structure, including variations in the B -site—O separation distances and the fact that 〈110〉 Pb 2+ displacements are most likely. A qualitative comparison between SCDS and the PDF shows that some features apparent in SCDS were not apparent in the PDF. These tended to pertain to short-range correlations in the structure, rather than to interatomic separations. For ex le, in SCDS the short-range alternation of the B -site cations was quite apparent in diffuse scattering at (½ ½ ½), whereas it was not apparent in the PDF.
A structure, conductivity and dielectric properties investigation of A(3)CoNb(2)O(9) (A = Ca2+, Sr2+, Ba2+) triple perovskites
Publisher: Elsevier BV
Date: 12-2004
Approaches to modelling thermal diffuse scattering in triglycine sulfate, (NH2CH2COOH)(3)center dot H2SO4
Publisher: International Union of Crystallography (IUCr)
Date: 22-02-2014
DOI: 10.1107/S1600576713034547
Abstract: The thermal diffuse scattering in triglycine sulfate, (NH 2 CH 2 COOH) 3 ·H 2 SO 4 , has been modelled by treating the intermolecular interactions that give rise to the correlated atomic displacements like Hooke's law springs. To limit the number of variables in the model, the force constants for the interactions were parameterized in a number of ways, the most successful of which was an empirical interaction potential using an exponential function of the interatomic separations.
The magnetic phase diagram of
Publisher: IOP Publishing
Date: 31-08-1998
Neutron diffuse scattering in deuterated para-terphenyl, C18D14
Publisher: IOP Publishing
Date: 25-02-2009
DOI: 10.1088/0953-8984/21/12/124204
Abstract: Neutron diffuse scattering is used to explore the short-range order (SRO) in deuterated para-terphenyl, C(18)D(14). The crystal shows SRO because the central of the three phenyl groups of each molecule can twist positively or negatively and these twists are correlated over the local scale. The presence of incipient Bragg peaks at [Formula: see text] at 200 K shows that these flips are negatively correlated along the a direction (nearest neighbour correlation coefficient of ∼-0.3) and b direction (nearest neighbour correlation coefficient of ∼-0.87) and appear essentially uncorrelated along c. Diffuse peak anisotropy indicates that the range of the correlations along b is found to be ∼3 times that along a. These correlations persist, although weaker, at room temperature. A Monte Carlo simulation was used to impose a correlation structure on the population of central ring twists that was deduced from Bragg scattering. By then allowing displacive relaxation of the structure, the observed diffuse scattering was well reproduced. Modelling the displacive motions of molecules showed that the positions of nearest ab-plane neighbour molecules are strongly positively correlated, particularly for motions approximately parallel to a, while the displacive correlations are weaker between molecules stacked along c. The apparent contradiction that the displacements are most strongly correlated along a while the occupancies are most strongly correlated along b is explained in terms of the connectivity of molecular interactions.
Diffuse scattering and partial disorder in complex structures
Publisher: International Union of Crystallography (IUCr)
Date: 28-10-2014
DOI: 10.1107/S205225251402065X
Abstract: The study of single-crystal diffuse scattering (SCDS) goes back almost to the beginnings of X-ray crystallography. Because SCDS arises from two-body correlations, it contains information about local (short-range) ordering in the s le, information which is often crucial in the attempt to relate structure to function. This review discusses the state of the field, including detectors and data collection and the modelling of SCDS using Monte Carlo and ab initio techniques. High-quality, three-dimensional volumes of SCDS data can now be collected at synchrotron light sources, allowing ever more detailed and quantitative analyses to be undertaken, and opening the way to approaches such as three-dimensional pair distribution function studies (3D-PDF) and automated refinement of a disorder model, powerful techniques that require large volumes of low-noise data.
Field-induced incommensurate spin structure of TbNiAl4
Publisher: American Physical Society (APS)
Date: 13-07-2012
Use of Monte Carlo simulation for the interpretation and analysis of diffuse scattering
Publisher: Informa UK Limited
Date: 02-2010
The Antiferromagnetic Structure of BaPrO3
Publisher: Elsevier BV
Date: 10-2004
Microstructure of Horseshoe Nails Using Neutron Diffraction
Publisher: Springer Science and Business Media LLC
Date: 02-07-2009
The impact of magnetic dilution on magnetic order in MnPS3
Publisher: IOP Publishing
Date: 08-05-2000
Monte Carlo study of disorder in HMTA
Publisher: Elsevier BV
Date: 12-2001
X-ray diffuse scattering from HMTA: Analysis via a Monte Carlo model
Publisher: International Union of Crystallography (IUCr)
Date: 14-06-2008
DOI: 10.1107/S0108768108010604
Abstract: Hexamethylenetetramine (HMT, C 6 H 12 N 4 , also referred to as urotropin) and azelaic acid [A, HOOC—(CH 2 ) 7 —COOH] form a co-crystal or adduct (HMTA, also referred to as urotropin azelate) which exhibits several structural phases as a function of temperature. At room temperature, the structure is orthorhombic, but shows substantial disorder. Here, this disorder is explored by analyzing the diffuse scattering from single crystals of HMTA via Monte Carlo simulation. The disorder is in part occupational, with two orientations of azelaic acid occurring, and in part thermally induced, which is to say dynamic. The occupational disorder can be thought of as a combination of limited-range in-plane ( bc plane) negative correlations combined with effectively zero correlation between planes (along a ), rather like stacking faults. Size effect, the cross-correlation between molecular orientation and displacement from average position, is required to reproduce the observed diffuse scattering.
Study of phase formation in metal injection moulding through real time neutron diffraction
Publisher: IOP Publishing
Date: 11-2010
Revealing How Interactions Lead to Ordering inPara-Terphenyl
Publisher: American Physical Society (APS)
Date: 09-01-2009
High-field magnetization in the diluted quasi-two-dimensional Heisenberg antiferromagnet Mn1 xZnxPS3
Publisher: IOP Publishing
Date: 05-09-2002
In vitro activities of miltefosine and two novel antifungal biscationic salts against a panel of 77 dermatophytes
Publisher: American Society for Microbiology
Date: 06-2007
DOI: 10.1128/AAC.01382-06
Abstract: The susceptibilities of 77 dermatophytes to miltefosine (MI), 1,12-bis(4-pentylpyridinium)dodecane (PYR), 1,12-bis(tributylammonium)dodecane (AM), itraconazole (ITC), terbinafine (TRB), and butenafine (BTF) were compared. Geometric mean MICs of TRB, BTF, ITC, MI, PYR, and AM were 0.039, 0.059, 1.718, 0.671, 6.006, and 4.771 μg/ml, respectively. MI was more active than ITC ( P 0.001).
Study of the single-crystal X-ray diffuse scattering in paracetamol polymorphs
Publisher: International Union of Crystallography (IUCr)
Date: 18-01-2012
DOI: 10.1107/S0108768111046295
Abstract: Single-crystal diffuse X-ray scattering from paracetamol polymorphs is successfully calculated with Monte Carlo (MC) models that are used to simulate the crystals. In order to obtain the correct model appropriate force constants are required that describe the interatomic potentials used in the MC algorithm. Coefficients for an empirical `Buckingham'-type formula are used to determine these force constants. These coefficients are subsequently refined using the least-squares method and are found to converge on similar values for both polymorphic forms. An investigation of the correlation space generated from each model provides what would be expected given that strong displacive correlations exist between the molecules comprising the densely hydrogen-bonded layers. More disordered motions between these layers are present in the model for form (II) as opposed to form (I). An investigation into the peculiarities of librational disorder was also conducted, however, correlation values turn out to be so small that any structural information concerning librational correlation is inconclusive. The purpose of this experiment was to identify if the diffuse scattering features could provide further insight into understanding the physical reasoning behind the metastability of form (II). The form (II) → (I) phase transition is also not currently well understood and usually phase transitional information can be obtained from pronounced diffuse scattering features. Since the diffuse scattering is modelled adequately using harmonic potentials it is our conjecture that the `diffuse' is essentially thermal in origin and does not afford any extra information about the form (II) → (I) phase transition.
Assessing Local Structure in PbZn1/3Nb2/3O3 Using Diffuse Scattering and Reverse Monte Carlo Refinement
Publisher: Springer Science and Business Media LLC
Date: 20-10-2012
A neutron diffraction study of the phase transition of fully deuterated triglycine sulphate (ND2CD2COOD)3.D2SO4
Publisher: Wiley
Date: 03-2013
Diffuse neutron scattering in benzil, C14 D10 O2 , using the time-of-flight Laue technique
Publisher: International Union of Crystallography (IUCr)
Date: 15-11-2003
DOI: 10.1107/S002188980302209X
Abstract: Diffuse neutron scattering data have been recorded for the molecular crystal d -benzil, C 14 D 10 O 2 , using the time-of-flight Laue technique on the SXD and PRISMA instruments at ISIS. Using SXD it was possible to access a large fraction of the total three-dimensional reciprocal space out to a Q value of 15 Å −1 , using only four in idual exposures and by making use of the \\bar{3}m Laue symmetry of the crystal. By segregating the scattered data according to the incident neutron energy used, patterns were obtained from those neutrons in the range of ∼20 meV to 150 meV, which showed little sign of inelastic effects and so could be compared with previously analysed X-ray data. For neutron energies of meV, interesting inelastic effects were observed, which have been used to obtain an estimate for the energy of phonons associated with a vibrational mode in which an intramolecular mode couples to a low-energy shearing motion of the hydrogen-bonded network linking neighbouring molecules. The estimated value of 8.95 cm −1 (1.11 meV) for this mode is less than the lowest energy mode reported from spectroscopic measurements for hydrogenous benzil (∼16 cm −1 ). A model previously derived from analysis of X-ray data observed over a limited range of Q has been used to calculate neutron patterns over the full Q range. Comparison with the present neutron data has shown that while the model gives a good description of the form of the diffuse patterns, the magnitudes of the atomic displacements are underestimated by a factor of ∼2.25.
Crystal field effects using polarised neutron spectroscopy
Publisher: Elsevier BV
Date: 10-1996
Problems in measuring diffuse X-ray scattering
Publisher: Walter de Gruyter GmbH
Date: 2005
A Quantum Multi-Critical Point in CeCu6-xAux
Publisher: Elsevier BV
Date: 11-2006
Monte Carlo Modelling of Single-Crystal Diffuse Scattering from Intermetallics
Publisher: MDPI AG
Date: 04-02-2016
DOI: 10.3390/MET6020033
Single-crystal diffuse scattering studies on polymorphs of molecular crystals. I. the room-temperature polymorphs of the drug benzocaine
Publisher: International Union of Crystallography (IUCr)
Date: 19-05-2009
DOI: 10.1107/S0108768109015857
Abstract: The drug benzocaine (ethyl 4-aminobenzoate), commonly used as a local anaesthetic, is a bimorphic solid at room temperature. Form (I) is monoclinic P 2 1 / c , while the metastable form (II) is orthorhombic P 2 1 2 1 2 1 . Three-dimensional diffuse X-ray scattering data have been collected for the two forms on the 11-ID-B beamline at the Advanced Photon Source (APS). Both forms show strong and highly structured diffuse scattering. The data have been interpreted and analysed using Monte Carlo (MC) modelling on the basis that the scattering is purely thermal in origin and indicates the presence of highly correlated molecular motions. In both forms (I) and (II) broad diffuse streaks are observed in the 0 kl section which indicate strong longitudinal displacement correlations between molecules in the 〈031〉 directions, extending over distances of up to 50 Å. Streaks extending between Bragg peaks in the hk 0 section normal to [100] correspond to correlated motions of chains of molecules extending along a that are linked by N—H...O=C hydrogen bonds and which occur together as coplanar ribbon pairs. The main difference between the two forms is in the dynamical behaviour of the ribbon pairs and in particular how they are able to slide relative to each other. While for form (I) a model involving harmonic springs is able to describe the motion satisfactorily, as simple excursions away from the average structure, there is evidence in form (II) of anharmonic effects that are precursors of a phase transition to a new low-temperature phase, form (III), that was subsequently found.
Crystal and magnetic structures in Perovskite-related (x=0.2, 0.33)
Publisher: Elsevier BV
Date: 12-2011
Crystal and magnetic structure of (1 - X) BiFeO 3-x SrTiO 3 (x=0.2, 0.3, 0.4 and 0.8)
Publisher: Elsevier BV
Date: 11-2013
Magnetic structure of TbNiAl4
Publisher: Elsevier BV
Date: 06-2006
Disorder in pentachloronitrobenzene, C6Cl5NO2: a diffuse scattering study
Publisher: International Union of Crystallography (IUCr)
Date: 17-07-2007
DOI: 10.1107/S0108768107024305
Abstract: Monte Carlo computer simulation has been used to interpret and model observed single-crystal diffuse X-ray scattering data for pentachloronitrobenzene, C 6 Cl 5 NO 2 . Each site in the crystal contains a molecule in one of six different basic orientations with equal probability. However, no short-range order amongst these different orientations has been detected. The strong, detailed and very distinctive diffraction patterns can be accounted for almost entirely on the assumption of random occupancy of each molecular site, but with very large local relaxation displacements that tend to increase the neighbouring distances for contacts involving NO 2 ...NO 2 and NO 2 ...Cl with a corresponding reduction for those involving Cl...Cl. The results show that the mean NO 2 ...NO 2 distance is increased by ∼ 0.6 Å, compared with that given by the average structure determination.
Local order in layered NiPS3 and Ni0.7 Mg 0.3 PS3
Publisher: IOP Publishing
Date: 25-01-2011
DOI: 10.1088/0953-8984/23/6/065401
Abstract: The family of two-dimensional magnetic materials M(II)PS(3) where M = Mn, Fe, Ni, Mg, Zn, etc shows a wide range of fascinating magnetic behaviour. It also shows potentially useful chemical properties including intercalation of nonlinear optical molecules and lithium ions. These properties are due to a crystal structure in which the ab planes are well-ordered in the plane but poorly correlated along c. Here, the short-range ordering is modelled in NiPS(3) and Ni(1 - x)Mg(x)PS(3) (x = 0.3). X-ray diffuse scattering from NiPS(3) shows pronounced streaking along c, indicative of stacking faulting in these layered compounds. Electron diffraction from Ni(1 - x)Mg(x)PS(3) (x = 0.3) shows substantial diffuse scattering due to short-range order within the ab plane, and this can be modelled by allowing the metal species to cluster. The possibility of clustering has implications for interpretation of the magnetic behaviour of the family, including the glassiness observed in Fe(1 - x)Mn(x)PS(3).
Atomic ordering in the doped rare earth cobaltates Ln0.33 Sr0.67 CoO3-δ (Ln = Y3+, Ho3+ and Dy3+)
Publisher: Elsevier BV
Date: 08-2003
Local order in wüstite using a pair distribution function (PDF) approach
Publisher: Mineralogical Society
Date: 04-2014
DOI: 10.1180/MINMAG.2014.078.2.10
Abstract: We show how different aspects of a model of the complex disordered structure of wüstite, Fe 1−x O, affect the pair distribution function (PDF) and powder diffraction pattern. The aim is to assess the efficacy of using these techniques to determine details of local structure. The different aspects include the nature of the in idual defect clusters, the nature of the paracrystalline superlattice on which they are distributed and the ‘size-effect’ relaxation of the basic rocksalt FeO matrix around the defects. The results show that PDF data are sensitive to those aspects of the models that have a significant effect on the populations of interatomic spacings but are less able to determine correlation structures in the s les if these do not have a substantial interaction with interatomic separations.
Exploring Cluster Growth Using a Simple Domino Tiling
Publisher: MDPI AG
Date: 04-05-2017
Interpretation of diffuse scattering in the high-T-c superconductor HgBa2CuO4+delta
Publisher: International Union of Crystallography (IUCr)
Date: 13-07-2016
DOI: 10.1107/S2052252516010629
Abstract: Published diffuse X-ray scattering from the high- T c superconductor HgBa 2 CuO 4+δ has been reexamined with a view to developing a model that more satisfactorily accounts for the observed patterns. The present work agrees with the previous conclusion that the doping oxygen atoms form long and isolated interstitial chains that run in both tetragonal directions. However, a distinctly different model is proposed for the accompanying displacement patterns of the atoms surrounding these linear defects. In this new model it is proposed that it is the correlated shifts of the Ba atoms along the length of the defect chains that are the primary source of the observed scattering, and that the variations of intensity in the generated diffuse streaks of scattering originate from lateral shifts of both Hg and Ba atoms away from defects. The new model yields diffraction patterns that are in much more convincing agreement with the observations than the original model.
A room-temperature X-ray diffuse scattering study of form (II) of the trimorphic molecular system p-(N-methylbenzylidene)-p-methylaniline
Publisher: International Union of Crystallography (IUCr)
Date: 15-09-2008
DOI: 10.1107/S0108768108023264
Abstract: Three-dimensional X-ray diffuse scattering data have been collected at room temperature for form (II) of the trimorphic molecular system p -( N -methylbenzylidene)- p -methylaniline. Although this polymorph has been reported to have a perfectly normal ordered average structure, strong and highly structured diffuse scattering was observed, indicating that substantial thermal disorder is present. A diffuse scattering analysis has been carried out using Monte Carlo simulation techniques. Narrow streaks of intensity extending between Bragg peaks in the h0l section were found to arise from planes of diffuse scattering in three dimensions. These are caused by highly correlated molecular displacements along chains of end-to-end disposed molecules running in the a\\!-\\!c direction, corresponding to methyl–methyl intermolecular interactions. A second significant feature – rods of diffuse scattering running in the b^* direction – indicates that molecular layers normal to b have a tendency to undergo lateral displacements with little correlation between layers. Finally, the internal flexibility of the molecule is required for a best fit. Changes in the two dihedral angles are found to be strongly correlated and show large excursions (\\gt\\pm20^{\\circ}) from the average values. All of these features suggest possible mechanisms for the way in which form (II) might transform to other polymorphs.
Monte Carlo Modeling of Diffuse Scattering from Single Crystals: The Program ZMC
Publisher: Springer Science and Business Media LLC
Date: 22-04-2010
Errata
Publisher: Springer Science and Business Media LLC
Date: 18-07-2009
The molecular conformation of Ibuprofen, C13 H18 O2 , through X-ray diffuse scattering
Publisher: Elsevier BV
Date: 10-2007
DOI: 10.1016/J.IJPHARM.2007.04.023
Abstract: A study of the three-dimensional distribution of the X-ray diffuse scattering from the pharmaceutical Ibuprofen (2-(4-isobutylphenyl)propionic acid, C(13)H(18)O(2)) has been undertaken. The most important aspects of the molecular flexibility have been isolated, as have key correlations between variables within a single molecule. Hence, aspects of the conformational space of the molecule within a crystalline environment have been outlined. For ex le the correlations between torsional twists on different bonds in the molecule (corresponding to the torsional angles on atoms C3, O1 and C11) have been established. Even though the atoms are on opposite sides of the phenyl group, there is a strong negative correlation between the torsional angle on C3 and that on C11. This shows that the ability to predict the conformation a fragment of a molecule will adopt based on the conformations of the fragment found in other molecules may be limited, as aspects of molecular geometry far from the fragment itself will have impact on its conformation. Between molecules, the positional coordinate components which coincide with the direction of propagation of strong intermolecular contacts, particularly the -COOH-HOOC- dimerising interactions, are positively correlated. On the other hand, motions perpendicular to such directions, and rotations about the torsional angles, do not propagate strongly from molecule to molecule.
Problems in measuring diffuse X-ray scattering
Publisher: Walter de Gruyter GmbH
Date: 12-2005
DOI: 10.1524/ZKRI.2005.220.12.1052
Abstract: Problems encountered in making measurements of diffuse X-ray scattering are discussed. These generally arise from the need to measure very weak scattering in the presence of very strong scattering (Bragg peaks) using multi-detectors of various kinds. The problems are not confined to synchrotron experiments but may even occur using a tube source in the home laboratory. Specific details are given of experiments using 80.725 keV X-rays and a mar345 Image Plate detector on the 1-ID beamline of XOR at the Advanced Photon Source. In these a severe ‘blooming’ artefact which occurred around some strong Bragg peaks was traced to fluorescence from a steel mounting plate in the detector when strong Bragg peaks were incident. Algorithms developed to remove these artefacts from the data are described.
Dr Trevor J Hicks
Publisher: IOP Publishing
Date: 19-01-2009
Optimising neutron polarisers—measuring a single cross-section
Publisher: Elsevier BV
Date: 09-2002
Chemical origin of nanoscale polar domains in PbZn1/3Nb2/3O3
Publisher: American Physical Society (APS)
Date: 21-12-2006
Use of bond-valence sums in modelling the diffuse scattering from PZN (PbZn1/3Nb2/3O3)
Publisher: International Union of Crystallography (IUCr)
Date: 11-10-2014
DOI: 10.1107/S2053273314016143
Abstract: This work extends previous efforts to model diffuse scattering from PZN (PbZn 1/3 Nb 2/3 O 3 ). Earlier work [Welberry et al. (2005). J. Appl. Cryst. 38 , 639–647 Welberry et al. (2006). Phys. Rev. B , 74 , 224108] is highly prescriptive, using Monte Carlo simulation with very artificial potentials to induce short-range-order structures which were deduced as necessary from inspection of the data. While this gives valid results for the nature of the local structure, it does not strongly relate these structures to underlying crystal chemistry. In that work, the idea of the bond-valence sum was used as a guide to the expected behaviour of the atoms. This paper extends the use of the bond-valence sum from a qualitative guide to becoming a key aspect of the potential experienced by the atoms, through the idea of the global instability index, whose square has been shown to be proportional to the density functional theory energy of some systems when close to the minimum energy configuration.
Distinguishing Types of Disorder in Diffuse Scattering: A Numerical Simulation Study
Publisher: Springer Science and Business Media LLC
Date: 06-2014
Magnetic structure and glassiness in
Publisher: Elsevier BV
Date: 05-2013
High-energy diffuse scattering on the 1-ID beamline at the Advanced Photon Source
Publisher: International Union of Crystallography (IUCr)
Date: 25-04-2003
DOI: 10.1107/S0909049503004643
Abstract: This paper reports on experiments in which high-energy (65.35 keV) X-rays were used to record the detailed diffuse diffraction patterns of a number of ceramic materials. The methodology has enabled a greater q-range to be explored (up to sintheta/lambda approximately 0.97) than is possible with laboratory-based experiments, with better q-space resolution and increased sensitivity, thus allowing previously unseen detail in diffraction patterns to be recorded. In all, 11 sections of data have been collected for Ca-CSZ, eight for Y-CSZ and six for wüstite.
Optimum thickness for neutron polarising filters
Publisher: Elsevier BV
Date: 06-1999
Spin-resolved neutron spectroscopy from the heavy Fermion compound CeCu6
Publisher: Elsevier BV
Date: 03-2004
Coupled Li1+/Nb5+ and O2-/F- ordering on the Na and Cl sites of the average NaCl structure of Li4NbO4F
Publisher: Elsevier BV
Date: 05-2009
Vapour diffusion growth and characterisation of fully deuterated triglycine sulphate (ND2CD2COOD)3D2SO4
Publisher: Elsevier BV
Date: 2012
Structural phase transition in d-benzil characterised by capacitance measurements and neutron powder diffraction
Publisher: Elsevier BV
Date: 12-2005
The influence of background on neutron polariser optimisation
Publisher: Springer Science and Business Media LLC
Date: 12-2002
Structure and magnetism in rare earth strontium-doped cobaltates
Publisher: Elsevier BV
Date: 11-2006
Evolution with applied field of the magnetic structure of TbNiAl4
Publisher: Springer Science and Business Media LLC
Date: 17-12-2014
Single-crystal neutron diffuse scattering and Monte Carlo study of the relaxor ferroelectric PbZn(1/3)Nb(2/3)O(3()PZN)
Publisher: International Union of Crystallography (IUCr)
Date: 13-07-2005
DOI: 10.1107/S0021889805015918
Abstract: Full three-dimensional diffuse neutron scattering data have been recorded from a single crystal of Pb(Zn 1/3 Nb 2/3 )O 3 (PZN) at 300 K using the time-of-flight Laue technique on the SXD single-crystal instrument at ISIS. The data show a series of diffuse rods of scattering oriented parallel to each of the six 〈1 1 0〉 crystal directions. Monte Carlo simulation has been used to demonstrate that the diffuse rods are caused by planar nanodomains oriented normal to the 〈1 1 0〉 directions. Within these domains, there are correlated displacements of the atoms away from their average site positions. In order to explain the systematic absence of some rods of scattering in the ( h k 1) data but the presence of all rods in the ( h k 0) data, it is necessary that the displacement of an O atom is of opposite sign to that of its neighbouring Pb atoms. This is explained in terms of a model based on the fact that Pb 2+ possesses a lone pair of electrons, giving the Pb ion directionality.
Different models for the polar nanodomain structure of PZN and other relaxor ferroelectrics
Publisher: International Union of Crystallography (IUCr)
Date: 14-05-2008
DOI: 10.1107/S0021889808012491
Abstract: Computer simulations have been carried out to test the recently proposed model for the nanodomain structure of relaxor ferroelectrics such as lead zinc niobate (PZN). In this recent model it was supposed that the polar nanodomains are three-dimensional, that the observed diffuse rods of scattering originate from the boundaries between domains and that the Pb displacements may be directed along \\langle {100} \\rangle, \\langle {111} \\rangle or \\langle {110} \\rangle. This is in marked contrast to a previously published model, which described the polar domains as thin plates with Pb displacements confined to the \\langle {110} \\rangle directions within the essentially two-dimensional domains. The present results confirm that \\langle {100} \\rangle and \\langle {111} \\rangle types of Pb displacement are viable possibilities, but the number of domain boundaries required to produce sufficiently strong diffuse rods of scattering means that in idual domains cannot be described as three-dimensional and must still be relatively thin. The current work has been carried out with no direct involvement of the B -site cation ordering, which many workers assume is necessary to understand the formation of the polar nanodomains. While it may be true that the B -site cation distribution could provide an underlying perturbation field that might ultimately limit the extent of any polar domain, it is certainly not necessary to produce the observed scattering effects.
The phase diagram and tetragonal superstructures of the rare earth cobaltate phases Ln1-x Srx CoO3-δ (Ln = La3+, Pr3+, Nd3+, Sm3+, Gd 3+, Y3+, Ho3+, Dy3+, Er 3+, Tm3+ and Yb3+)
Publisher: Elsevier BV
Date: 06-2004
Dipolar anisotropy in quasi-2D honeycomb antiferromagnet MnPS3
Publisher: Springer Science and Business Media LLC
Date: 12-11-2010
Ordering and the nature of the spin flop phase transition in MnPS3
Publisher: IOP Publishing
Date: 10-02-2000
Structural phase transition in deuterated benzilC 14
Publisher: American Physical Society (APS)
Date: 26-04-2006
Modelling disorder in 3,3′-dimethoxybenzil, C16 H 14 O4
Publisher: Walter de Gruyter GmbH
Date: 2005
neutron polarising filters — theoretical comparison with supermirrors and Heusler alloy polarisers
Publisher: Elsevier BV
Date: 02-2000
Structure and magnetism in the oxygen-deficient perovskites Ce 1-x Srx CoO3-δ (x ≥ 0.90)
Publisher: Elsevier BV
Date: 08-2005
Nanoscale Order in Molecular Systems from Single Crystal Diffuse Scattering
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/CH14229
Abstract: Diffuse scattering – the coherently scattered intensity that is not localised on the reciprocal lattice – contains a wealth of information about the local order (order on the nanoscale) in crystalline materials. Since molecules and atoms will respond most strongly to their local chemical environments, it is a valuable tool in understanding how structure leads to properties. However, at present its collection and analysis are relatively specialised. Monte Carlo (MC) computer simulation of a model structure has become a powerful and well-accepted technique for aiding the interpretation and analysis of diffuse scattering patterns. Its great strength is its flexibility – as long as an MC energy can be defined, a model can be developed and tested. At one extreme a very simplified model may be useful in demonstrating particular qualitative effects, while at the other a quantitative and very detailed description of disordered structures can be obtained. Ex les discussed include new results concerning p-chloro-N-(p-chloro-benzylidene)aniline, a molecule showing various degrees of molecular flexibility.
A refinement strategy for Monte Carlo modelling of diffuse scattering from molecular crystal systems
Publisher: International Union of Crystallography (IUCr)
Date: 07-2010
DOI: 10.1107/S0021889810022260
Abstract: A new strategy for modelling diffuse scattering from molecular crystals using Monte Carlo simulation is described. The use of harmonic (Hooke's law) springs to represent effective intermolecular interactions is preserved, in order to minimize computer requirements, but use is now made of a simple empirical formula to specify spring constants and provide an objective means for limiting the number of springs needed to be used. The method has been tested on diffuse scattering data obtained for form I of paracetamol.
The interpretation and analysis of diffuse scattering using Monte Carlo simulation methods
Publisher: International Union of Crystallography (IUCr)
Date: 21-12-2008
DOI: 10.1107/S0108767307041918
Abstract: Studies of diffuse scattering had a prominent place in the first issue of Acta Crystallographica 60 years ago at a time when conventional crystallography (determination of the average structure from Bragg peaks) was in its infancy. Since that time, conventional crystallography has developed enormously while diffuse-scattering analysis has seemingly lagged well behind. The paper highlights some of the extra difficulties involved in the measurement, interpretation and analysis of diffuse scattering and plots the progress that has been made. With the advent of the latest X-ray and neutron sources, area detectors and the ever-increasing power of computers, most disorder problems are now tractable. Two recent contrasting ex les are described which highlight what can be achieved by current methods.
Contrasting antiferromagnetic order between FePS 3 and MnPS 3
Publisher: Springer Science and Business Media LLC
Date: 12-2002
Chemical and magnetic ordering in Fe0.5Ni0.5 PS 3
Publisher: Springer Science and Business Media LLC
Date: 18-12-2014
A computational model of gastro-intestinal motility
Publisher: Elsevier BV
Date: 12-2001
Synchrotron X-ray diffuse scattering from a stable polymorphic material: terephthalic acid, C8H6O4
Publisher: International Union of Crystallography (IUCr)
Date: 31-01-2017
DOI: 10.1107/S2052520616018801
Abstract: Terephthalic acid (TPA, C 8 H 6 O 4 ) is an industrially important chemical, one that shows polymorphism and disorder. Three polymorphs are known, two triclinic [(I) and (II)] and one monoclinic (III). Of the two triclinic polymorphs, (II) has been shown to be more stable in ambient conditions. This paper presents models of the local order of polymorphs (I) and (II), and compares the single-crystal diffuse scattering (SCDS) computed from the models with that observed from real crystals. TPA shows relatively weak and less-structured diffuse scattering than some other polymorphic materials, but it does appear that the SCDS is less well modelled by a purely harmonic model in polymorph (I) than in polymorph (II), according to the idea that the diffuse scattering is sensitive to anharmonicity that presages a structural phase transition. The work here verifies that displacive correlations are strong along the molecular chains and weak laterally, and that it is not necessary to allow the —COOH groups to librate to successfully model the diffuse scattering – keeping in mind that the data are from X-ray diffraction and not directly sensitive to H atoms.
Optimising Sintering in Metal Injection Moulding Using In Situ Neutron Diffraction
Publisher: Trans Tech Publications, Ltd.
Date: 2012
DOI: 10.4028/WWW.SCIENTIFIC.NET/MSF.706-709.1737
Abstract: The phase evolution during the sintering of metal injection moulded stainless steel, 316Land 17-4PH, has been observed using in situ neutron diffraction and Rietveld analysis. The formationof the ferrite phase in the final product is associated with the production of -ferrite at high temperatures.Coexistence of phases at high temperature is thought to allow the segregation of alloyingelements, stabilising the ferrite to lower temperature. To prevent ferrite in the final products the sinteringmust occur at a lower temperature than that at which -ferrite is formed. An alternative regimeis proposed in which the temperature would be cycled around the formation temperature of -ferrite.
Monte Carlo Simulation Study of Diffuse Scattering in PZT, Pb(Zr,Ti)O-3
Publisher: Springer Science and Business Media LLC
Date: 27-05-2010
Long peripheral catheters in children: A scoping review
Publisher: Wiley
Date: 27-09-2022
DOI: 10.1002/JHM.12968
Abstract: Long peripheral catheters (LPCs) are emerging vascular access devices used for short‐medium term vascular access needs. Literature in adults suggests LPCs have longer dwell‐times than peripheral intravenous catheters (PIVs) and lower rates of serious complications than peripherally inserted central catheters (PICCs). The role of LPCs in children is less established. The objective of this scoping review is to describe and synthesize the existing literature on the effectiveness and safety of LPCs in children. This review follows the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses extension for Scoping Reviews (PRISMA‐ScR) guidelines. Searches were done in MEDLINE (Ovid), Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science Core Collection, Scopus, CINAHL (Ebsco), and Google Scholar most recently on February 22, 2022. Studies were included if published in English on or after 2000 and included patients years of age. Twenty‐one studies were included. The body of literature is variable in quality, measurements, and reported outcomes. Median dwell‐time ranged from 5 to 14 days. The rate of completion of therapy ranged from 20% to 86%. Dislodgement, occlusion, and infiltration were the most common complications reported (0%–31%). Venous thromboembolism rates ranged from 0% to 13%. The rate of catheter‐related bloodstream infection was 0% in 9 of 10 studies. Less than 50% of studies reported comparative outcomes. LPCs show promising outcomes in select populations, with longer dwell‐time than PIVs and possibly lower rates of serious complications than PICCs. However, more research is needed to clarify the optimal use of LPCs in pediatrics.
Diffuse scattering study of aspirin forms (I) and (II)
Publisher: International Union of Crystallography (IUCr)
Date: 10-11-2010
DOI: 10.1107/S0108768110037055
Abstract: Full three-dimensional diffuse scattering data have been recorded for both polymorphic forms [(I) and (II)] of aspirin and these data have been analysed using Monte Carlo computer modelling. The observed scattering in form (I) is well reproduced by a simple harmonic model of thermally induced displacements. The data for form (II) show, in addition to thermal diffuse scattering (TDS) similar to that in form (I), diffuse streaks originating from stacking fault-like defects as well as other effects that can be attributed to strain induced by these defects. The present study has provided strong evidence that the aspirin form (II) structure is a true polymorph with a structure quite distinct from that of form (I). The diffuse scattering evidence presented shows that crystals of form (II) are essentially composed of large single domains of the form (II) lattice with a relatively small volume fraction of intrinsic planar defects or faults comprising misoriented bilayers of molecular dimers. There is evidence of some local aggregation of these defect bilayers to form small included regions of the form (I) structure. Evidence is also presented that shows that the strain effects arise from the mismatch of molecular packing between the defect region and the surrounding form (II) lattice. This occurs at the edges of the planar defects in the b direction only.
Simultaneous fitting of X-ray and neutron diffuse scattering data
Publisher: International Union of Crystallography (IUCr)
Date: 19-12-2007
Structural and magnetic properties ofY0.33Sr0.67CoO2.79
Publisher: American Physical Society (APS)
Date: 06-04-2004
Monte Carlo analysis of neutron diffuse scattering data
Publisher: Elsevier BV
Date: 11-2006
A method to perform modulated structure studies using the program ZMC
Publisher: International Union of Crystallography (IUCr)
Date: 20-11-2017
DOI: 10.1107/S1600576717015023
Abstract: The Monte Carlo simulation toolkit ZMC provides a general method for Monte Carlo simulation of disordered molecular displacements, orientations and site occupations. It is part of a suite of programs that allows convenient calculation of three-dimensional reciprocal space diffraction intensities. Such intensities are useful for extensive structure interpretations from diffraction experiments. Some physical properties can also be calculated from the simulation. This article reports the implementation of an integrated ZMC module that facilitates the construction of modulated molecular crystals and allows the corresponding calculation of modulation satellites. Use of the module is explained and ex les illustrated. The method is ideally suited for novice treatment of modulated structure features and also as a basic platform to explore complex structure roperties relationships using atomistic simulation techniques.
Optimising neutron polarizers—measuring the flipping ratio and related quantities
Publisher: Elsevier BV
Date: 04-2002
Optimising polarised neutron scattering measurements—XYZ and polarimetry analysis
Publisher: Elsevier BV
Date: 09-2002
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Australian Nuclear Science And Technology Organisation
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