PDFfit2 and PDFgui: computer programs for studying nanostructure in crystals

Farrow, Christopher L.; Juhás, Pavol; Liu, J W; Bryndin, D; Božin, Emil S.; Bloch, Jacques; Proffen, Thomas; Billinge, Simon J. L.

doi:10.1088/0953-8984/19/33/335219

Cited by 1,628 publications

(1,822 citation statements)

References 27 publications

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“…43,44 The local structure was investigated via analysis of the real-space PDF using the PDFgui software suite. 45 Correlated motion in the PDF was modeled using the sratio and rcut parameters, which account for effects on the PDF due to correlated motion of rigid structural units. An rcut value of 5Å was specified, which corresponds to the approximate Br-Br distance in the SnBr 6 .…”

Section: Methodsmentioning

confidence: 99%

Dynamic Stereochemical Activity of the Sn²⁺ Lone Pair in Perovskite CsSnBr₃

et al. 2016

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Stable s 2 lone pair electrons on heavy main-group elements in their lower oxidation states drive a range of important phenomena, such as the emergence of polar ground states in some ferroic materials. Here we study the perovskite halide CsSnBr 3 as an embodiment of the broader materials class. We show that lone pair stereochemical activity due to the Sn s 2 lone pair causes a crystallographically hidden, locally distorted state to appear upon warming, a phenomenon previously referred to as emphanisis.The synchrotron X-ray pair distribution function acquired between 300 K and 420 K reveals emerging asymmetry in the nearest-neighbor Sn-Br correlations, consistent with dynamic Sn 2+ off-centering, despite there being no evidence of any deviation from the average cubic structure. Computation based on density functional theory supports the finding of a lattice instability associated with dynamic off-centering of Sn 2+ in its coordination environment. Photoluminescence measurements reveal an unusual blueshift with increasing temperature, closely linked to the structural evolution. At low temperatures, the structures reflect the influence of octahedral rotation. A continuous transition from an orthorhombic structure (P nma, no. 62) to a tetragonal structure (P 4/mbm, no. 127) is found around 250 K, with a final, first-order transformation at 286 K to the cubic structure (P m3m, no. 221).2

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Section: Methodsmentioning

confidence: 99%

Dynamic Stereochemical Activity of the Sn²⁺ Lone Pair in Perovskite CsSnBr₃

et al. 2016

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“…Least-squares refinements were performed on the PDF to obtain local structure information using PDFgui. 33 The real-space instrument parameters Q damp and Q broad were determined from a crystalline material calibration standard and fixed at 0.00623Å −1 and 0.0021Å −1 , respectively. Refinement ranges of 1Å to r max , with r max = 5Å, 10Å, 15Å, 20Å, and 50Å, were chosen to explore the effects of diffuse thermal scattering and correlated motion on the local structure and the average structure.…”

Section: Methodsmentioning

confidence: 99%

Average and Local Structure, Debye Temperature, and Structural Rigidity in Some Oxide Compounds Related to Phosphor Hosts

Denault

Brgoch

Kloß

et al. 2015

ACS Appl. Mater. Interfaces

182

121

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The average and local structure of the oxides Ba2SiO4, BaAl2O4, SrAl2O4, and Y2SiO5 are examined to evaluate crystal rigidity in light of recent studies suggesting that highly connected and rigid structures yield the best phosphor hosts. Simultaneous momentum-space refinements of synchrotron X-ray and neutron scattering yield accurate average crystal structures, with reliable atomic displacement parameters. The Debye temperature ΘD, which has proven to be a useful proxy for structural rigidity, is extracted from the experimental atomic displacement parameters and compared with predictions from density functional theory calculations and experimental low-temperature heat capacity measurements. The role of static disorder on the measured displacement parameters, and the resulting Debye temperatures, are also analyzed using pair distribution function of total neutron scattering, as refined over varying distance ranges of the pair distribution function. The interplay between optimal bonding in the structure, structural rigidity, and correlated motion in these structures is examined, and the different contributions are delineated.

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“…PDF approximately matches the periodic atomic arrangement associated with the present cubic crystal structures (B2, BCC and FCC). Here, the fitting model, implemented using the PDFgui software package 43 , represents the ideal structure, where the equilibrium position of each atom falls exactly on its assigned lattice site. Comparing with the observed PDF, the greatest mismatch occurs at short distances, less than 10 Å, suggesting the presence of local lattice distortions due to different atomic sizes in the solid solution 24 .…”

Section: Room Temperature Microstructuresmentioning

confidence: 99%

Deviation from high-entropy configurations in the atomic distributions of a multi-principal-element alloy

et al. 2015

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The alloy-design strategy of combining multiple elements in near-equimolar ratios has shown great potential for producing exceptional engineering materials, often known as 'high-entropy alloys'. Understanding the elemental distribution, and, thus, the evolution of the configurational entropy during solidification, is undertaken in the present study using the Al 1.3 CoCrCuFeNi model alloy. Here we show that, even when the material undergoes elemental segregation, precipitation, chemical ordering and spinodal decomposition, a significant amount of disorder remains, due to the distributions of multiple elements in the major phases. The results suggest that the high-entropy alloy-design strategy may be applied to a wide range of complex materials, and should not be limited to the goal of creating single-phase solid solutions.

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PDFfit2 and PDFgui: computer programs for studying nanostructure in crystals

Cited by 1,628 publications

References 27 publications

Dynamic Stereochemical Activity of the Sn²⁺ Lone Pair in Perovskite CsSnBr₃

Dynamic Stereochemical Activity of the Sn²⁺ Lone Pair in Perovskite CsSnBr₃

Average and Local Structure, Debye Temperature, and Structural Rigidity in Some Oxide Compounds Related to Phosphor Hosts

Deviation from high-entropy configurations in the atomic distributions of a multi-principal-element alloy

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PDFfit2 and PDFgui: computer programs for studying nanostructure in crystals

Cited by 1,628 publications

References 27 publications

Dynamic Stereochemical Activity of the Sn2+ Lone Pair in Perovskite CsSnBr3

Dynamic Stereochemical Activity of the Sn2+ Lone Pair in Perovskite CsSnBr3

Average and Local Structure, Debye Temperature, and Structural Rigidity in Some Oxide Compounds Related to Phosphor Hosts

Deviation from high-entropy configurations in the atomic distributions of a multi-principal-element alloy

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Dynamic Stereochemical Activity of the Sn²⁺ Lone Pair in Perovskite CsSnBr₃

Dynamic Stereochemical Activity of the Sn²⁺ Lone Pair in Perovskite CsSnBr₃