Estimating temperature-dependent anisotropic hydrogen displacements with the invariom database and a new segmented rigid-body analysis program

Invariom partitioning and notation are used to estimate anisotropic hydrogen displacements for incorporation in crystallographic refinement models. Optimized structures of the generalized invariom database and their frequency computations provide the information required: frequencies are converted to internal atomic displacements and combined with the results of a TLS (translation–libration–screw) fit of experimental non-hydrogen anisotropic displacement parameters to estimate those of H atoms. Comparison with TLS+ONIOM and neutron diffraction results for four example structures where high-resolution X-ray and neutron data are available show that electron density transferability rules established in the invariom approach are also suitable for streamlining the transfer of atomic vibrations. A new segmented-body TLS analysis program calledAPD-Toolkithas been coded to overcome technical limitations of the established programTHMA. The influence of incorporating hydrogen anisotropic displacement parameters on conventional refinement is assessed.

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Non-ambient X-ray and neutron diffraction of novel relaxor ferroelectric xBi2(Zn2/3,Nb1/3)O3–(1 – x)BaTiO3

Journal of Applied Crystallography ◽

10.1107/s160057672100858x ◽

2021 ◽

Vol 54 (5) ◽

Author(s):

Jessica Marshall ◽

David Walker ◽

Pamela Thomas

Keyword(s):

Neutron Diffraction ◽

Lattice Parameter ◽

The Novel ◽

Temperature Dependent ◽

Low Loss ◽

Neutron Data ◽

Ferroelectric Relaxor ◽

X Ray ◽

Unit Cells

The first determination of the phase diagram of the novel ferroelectric relaxor xBi(Zn2/3Nb1/3)O3–(1 − x)BaTiO3 (BZN-BT) has been achieved with a combination of high-resolution X-ray and neutron diffraction up to the miscibility limit near x(BZN) = 20.0% over a temperature range 20 < T < 400 K. The combined X-ray and neutron data show that the instability within the xBZN-(1−x)BT system reaches a maximum at x = 3.9% and is driven by B-site displacement and distortion of the oxygen octahedra in the polar phases. Composition-dependent effects include a narrow Amm2-dominated region focused at x = 3.9%, significant convergence of the lattice parameters in both P4mm and Amm2 phases, and sharp maxima in piezoelectric coefficient d 33 and maximum polarization P max. Lattice parameter dilation at x ≥ 4.0% was observed for both P4mm and Amm2 unit cells, alongside the first appearance of Pm 3 m at 295 K and the onset of significant dielectric relaxation. Low-temperature neutron diffraction indicated a weak or non-existent temperature dependence on the transition from ferroelectric at x = 3.9% to ferroelectric relaxor at x = 4.0%. Temperature-dependent phase transitions were eliminated near x = 3.0%, with the ferroelectric limit observed at x = 5.0% and a transition to a low-loss relaxor dielectric near x = 8.0%.

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Atomic displacements in BiFeO3 as a function of temperature: neutron diffraction study

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768107023956 ◽

2007 ◽

Vol 63 (4) ◽

pp. 537-544 ◽

Cited By ~ 146

Author(s):

A. Palewicz ◽

R. Przeniosło ◽

I. Sosnowska ◽

A. W. Hewat

Keyword(s):

Crystal Structure ◽

High Resolution ◽

Neutron Diffraction ◽

Local Minimum ◽

Local Maximum ◽

Neutron Diffraction Study ◽

Electric Polarization ◽

Neutron Powder Diffraction ◽

Atomic Displacements ◽

Atomic Vibrations

The parameters of the crystal structure of BiFeO3, described within the space group R3c, have been determined by high-resolution neutron powder diffraction for temperatures from 293 to 923 K. It was found that there is a local minimum for the rhombohedral angle αrh, near the Néel temperature T N ≃ 640 K, a gradual rotation of the FeO6 octahedra and an increase of the Fe—O—Fe angle. The displacement of the Bi3+ ions from the FeO6 octahedra which influence the electric polarization decreases with temperature. One of the Bi—Fe distances also has a local maximum near T N. The atomic vibrations of Bi3+ and O2− ions show a significant anisotropy.

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Investigation of Residual Strains of the Second Kind in Plastically Deformed Metallic Materials

MRS Proceedings ◽

10.1557/proc-376-409 ◽

1994 ◽

Vol 376 ◽

Cited By ~ 2

Author(s):

M. Vrána ◽

P. Klimanek ◽

T. Kschidock ◽

P. Lukáš ◽

P. Mikula

Keyword(s):

High Resolution ◽

Neutron Diffraction ◽

Stacking Faults ◽

Metallic Materials ◽

Line Broadening ◽

X Ray Diffraction ◽

X Ray ◽

Neutron Diffractometer ◽

Residual Strains ◽

Good Agreement

ABSTRACTInvestigation of strongly distorted crystal structures caused by dislocations, stacking-faults etc. in both plastically deformed f.c.c. and b.c.c. metallic materials was performed by the analysis of the neutron diffraction line broadening. Measurements were realized by means of the high resolution triple-axis neutron diffractometer equipped by bent Si perfect crystals as monochromator and analyzer at the NPI Řež. The substructure parameters obtained in this manner are in good agreement with the results of X-ray diffraction analysis.

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Lower resolution Laue neutron data yield correct nanocluster formulations

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s205327331409812x ◽

2014 ◽

Vol 70 (a1) ◽

pp. C187-C187

Author(s):

Alison Edwards

Keyword(s):

Neutron Diffraction ◽

Single Crystal ◽

Diffraction Pattern ◽

Precise Determination ◽

Data Sets ◽

X Rays ◽

Low Resolution ◽

Neutron Data ◽

X Ray ◽

Product Formulation

"The renaissance in Laue studies - at neutron sources - provides us with access to single crystal neutron diffraction data for synthetic compounds without requiring synthesis of prohibitively large amounts of compound or improbably large crystals. Such neutron diffraction studies provide vital data where proof of the presence or absence of hydrogen in particular locations is required and which cannot validly be proved by X-ray studies. Since the commissioning of KOALA at OPAL in 2009[1] we have obtained numerous data sets which demonstrate the vital importance of measuring data even where the extent of the diffraction pattern is at relatively low resolution - especially when compared to that obtainable for the same compound with X-rays. In the Laue experiment performed with a fixed radius detector, data reduction is only feasible for crystals in the ""goldilocks"" zone – where the unit cell is relatively large for the detector, a correspondingly low resolution diffraction pattern in which adjacent spots are less affected by overlap will yield more data against which a structure can be refined than a pattern of higher resolution – one where neighbouring spots overlap rendering both unusable (in our current methodology). Analogous application of powder neutron diffraction in such determinations is also considered. Single crystal neutron diffraction studies of several important compounds (up to 5KDa see figure below)[2] in which precise determination of hydride content by neutron diffraction was pivotal to the final formulation will be presented. The neutron data sets typically possess 20% or fewer unique data at substantially "lower resolution" than the corresponding X-ray data sets. Careful refinement clearly reveals chemical detail which is typically unexplored in related X-ray diffraction studies reporting high profile chemistry despite the synthetic route being one which hydride ought to be considered/excluded in product formulation."

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Ultra high resolution X-ray and neutron diffraction studies of fully deuterated aldose reductase show a catalytic proton pathway

Acta Crystallographica Section A Foundations of Crystallography ◽

10.1107/s0108767306099612 ◽

2006 ◽

Vol 62 (a1) ◽

pp. s19-s19

Author(s):

F. Ruiz ◽

A. Mitschler ◽

I. Hazemann ◽

M. Blakely ◽

M.-T. Dauvergne ◽

...

Keyword(s):

High Resolution ◽

Neutron Diffraction ◽

Aldose Reductase ◽

X Ray

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Neutron diffraction refinement and high resolution X-ray study of crystal structure of LiND4SO4 (DLAS)

Physica B Condensed Matter ◽

10.1016/0921-4526(89)90605-4 ◽

1989 ◽

Vol 156-157 ◽

pp. 118-120 ◽

Cited By ~ 6

Author(s):

P. Fischer ◽

I. Sosnowska ◽

T. Wroblewski

Keyword(s):

Crystal Structure ◽

High Resolution ◽

Neutron Diffraction ◽

X Ray

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Single-crystal neutron diffraction study of β-Cs3(HSO4)2[H2−x (S x P1−x )O4] (x ≃ 0.5) at 15 K

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768198013573 ◽

1999 ◽

Vol 55 (3) ◽

pp. 285-296 ◽

Cited By ~ 6

Author(s):

S. M. Haile ◽

W. T. Klooster

Keyword(s):

Neutron Diffraction ◽

Single Crystal ◽

Local Structure ◽

Unit Cell Volume ◽

Structural Models ◽

Neutron Diffraction Study ◽

Unit Cell ◽

Asymmetric Unit ◽

X Ray ◽

Anisotropic Displacement Parameters

The structure of β-Cs3(HSO4)2[H2−x (S x P1−x )O4] has been examined by single-crystal neutron diffraction at 15 K. The compound crystallizes in space group C2/c and contains four formula units in the unit cell, with lattice parameters a = 19.769 (9), b = 7.685 (2), c = 8.858 (3) Å and β = 100.60 (4)°. Refinement of P, S and H site occupancies indicated that the value of x (in the stoichiometry) is 0.500 (6). This, together with the unit-cell volume of 1322.8 (14) Å3, implies a density of 3.463 Mg m−3. The structure contains zigzag rows of XO4 anions, where X = P or S, that alternate, in a checkerboard fashion, with zigzag rows of Cs cations. Moreover, there is one proton site, H(3), with an occupancy of 0.25 and one X-atom site, X(1), that is occupied by 0.5 P and 0.5 S. These features are in general agreement with a previous X-ray structure determination carried out at 298 K. In contrast to the X-ray study, however, it was found that two different structural models adequately fit the diffraction data. In the first model, the proton vacancies and the P atoms were assumed to be randomly distributed over the H(3) and X(1) sites, respectively, and to have no impact on the local structure. In the second model, several atoms were assigned split occupancies over two neighboring sites, to reflect the presence or absence of a proton vacancy, and the presence of P or S on the X(1) site. Refinement assuming the first model, in which anisotropic displacement parameters for 12 of 14 atom sites in the asymmetric unit were employed, yielded residuals w R(F 2) = 0.084 and w R(F) = 0.038. For the second model, in which anisotropic displacement parameters were utilized for only the five atoms that were not split relative to the first model, the residuals were w R(F 2) = 0.081 and w R(F) = 0.036.

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Engineering short, strong hydrogen bonds in urea di-carboxylic acid complexes

CrystEngComm ◽

10.1039/c4ce00587b ◽

2014 ◽

Vol 16 (35) ◽

pp. 8177-8184 ◽

Cited By ~ 17

Author(s):

Andrew O. F. Jones ◽

Charlotte K. Leech ◽

Garry J. McIntyre ◽

Chick C. Wilson ◽

Lynne H. Thomas

Keyword(s):

Hydrogen Bond ◽

Carboxylic Acid ◽

Hydrogen Bonds ◽

Neutron Diffraction ◽

Structural Changes ◽

Acid Amide ◽

Molecular Complexes ◽

Temperature Dependent ◽

X Ray ◽

Methyl Substitution

The persistence of the acid⋯amide heterodimer and the effect of methyl substitution on the short strong O–H⋯O hydrogen bond is investigated in urea and methylurea di-carboxylic acid molecular complexes. Temperature dependent structural changes are also reported utilising X-ray and neutron diffraction in tandem.

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