Recent Developments in the Refinement and Analysis of Crystal Structures

Cooper, Richard I.

doi:10.1007/430_2020_76

Cited by 3 publications

(1 citation statement)

References 54 publications

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“…In crystallographically ordered materials, the representation of the scattering density in terms of atomic ellipsoids is essentially unique [28]. In the context of disordered materials, however, several equally valid representations of the same scattering density may be possible; an unwary scientist may take the differences between these representations more seriously than the underlying data warrant.…”

Section: Crystallographymentioning

confidence: 99%

On (not) deriving the entropy of barocaloric phase transitions from crystallography and neutron spectroscopy

Phillips,

Walker

2023

J. Phys. Energy

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We consider well-known signatures of disorder in crystallographic and inelastic neutron scattering data. We show that these can arise from different types of disorder, corresponding to different values of the system entropy. Correlating the entropy of a material with its atomistic structure and dynamics is in general a difficult problem that requires correlating information between multiple experimental techniques including crystallography, spectroscopy, and calorimetry. These comments are illustrated with particular reference to barocalorics, but are relevant to a broad range of calorics and other disordered crystalline materials.

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Section: Crystallographymentioning

confidence: 99%

On (not) deriving the entropy of barocaloric phase transitions from crystallography and neutron spectroscopy

Phillips,

Walker

2023

J. Phys. Energy

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Are Monophospha(III)amidines and ‐guanidines with Ionizable Hydrogens Tautomeric? Towards a Deeper Understanding of Two Related Hetero‐element Functional Groups

Masuda,

Mokhtabad Amrei,

Boeré

2023

Eur J Inorg Chem

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This paper presents definitive structural evidence for N,P(III)‐monophosphaamidines in P=C and N=C isomeric forms from a combination of new syntheses, single‐crystal X‐ray diffraction (SC‐XRD), solid‐state NMR and FTIR. Evidence is also provided for C‐amino‐(σ2,λ3)‐phosphaalkene and C‐(σ3,λ3)‐phosphinoimine tautomerism in solution using multi‐nuclear NMR methods. Synthesis and SC‐XRD structure determination of a trisubstituted N,N’,P(III)‐monophosphaguanidine is presented, the first structure of a phospha(III)guanidine with two ionizable H atoms. The structural evidence is convincing for an N=C geometry, resulting in both N−H and P−H in the molecule. A detailed computational investigation using DFT methods is presented, with the goal of understanding the tautomeric structure preferences both at the fundamental level (parent molecules with all substituents on the heteroatoms being hydrogen) and using the full structures containing the very bulky 2,6‐diisopropylphenyl (Dipp) substituents employed in this study. Arguments are espoused for treating phospha(III)amidines and ‐guanidines as new types of functional groups, similar to but distinct from the familiar organic analogues. Limited reactivity studies and a voltammetry study of one phospha(III)amidine are included with the supporting information.

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Crystal Structures of CuCl2·2H2O (Eriochalcite) and NiCl2∙6H2O (Nickelbischofite) at Low Temperature: Full Refinement of Hydrogen Atoms Using Non-Spherical Atomic Scattering Factors

Boeré

2023

Crystals

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New structure determinations of CuCl2∙2H2O and NiCl2∙6H2O are reported from 100 K X-ray diffraction experiments using both Mo Kα and Cu Kα radiation. Combined density functional theory (ORCA) and non-spherical atomic scattering factor (NoSpherA2) computations enabled Hirshfeld atom refinements (HAR) using custom atom scattering factors based on accurately polarized atom electron densities. The water hydrogen atoms could be positionally refined resulting in distinctly longer O–H bond lengths than those reported from previous X-ray diffraction experiments, but in good agreement with legacy neutron diffraction studies. Anisotropic displacement factors were employed, for the first time in these compounds by any technique. The outcomes from using the different X-ray sources with this new HAR method are compared, and the precision of the H-atom refinements evaluated where possible.

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Recent Developments in the Refinement and Analysis of Crystal Structures

Cited by 3 publications

References 54 publications

On (not) deriving the entropy of barocaloric phase transitions from crystallography and neutron spectroscopy

On (not) deriving the entropy of barocaloric phase transitions from crystallography and neutron spectroscopy

Are Monophospha(III)amidines and ‐guanidines with Ionizable Hydrogens Tautomeric? Towards a Deeper Understanding of Two Related Hetero‐element Functional Groups

Crystal Structures of CuCl2·2H2O (Eriochalcite) and NiCl2∙6H2O (Nickelbischofite) at Low Temperature: Full Refinement of Hydrogen Atoms Using Non-Spherical Atomic Scattering Factors

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