Elastic stiffness coefficients of thiourea from thermal diffuse scattering

Büscher, Julia; Mirone, Alessandro; Stękiel, Michał; Spahr, Dominik; Morgenroth, Wolfgang; Haussühl, Eiken; Milman, Victor; Bosak, Alexeï; Ivashko, Oleh; Zimmermann, M. v.; Dippel, Ann‐Christin; Winkler, Björn

doi:10.1107/s1600576720016039

“…For example, ISTS measurements have been performed on polished thin slabs 600–800 μm thick for the explosives PETN and RDX, [27] enabling a critical comparison with previous ultrasonic, RUS and Brillouin scattering results, and this comparison is discussed in detail in Section 5.14. Less commonly, elastic tensors have also been obtained from the thermal diffuse scattering of X‐rays, [28–33] and from inelastic neutron scattering [34] …”

Section: Introductionmentioning

confidence: 99%

Quantifying Mechanical Properties of Molecular Crystals: A Critical Overview of Experimental Elastic Tensors

Spackman

¹

,

Grosjean

²

,

Thomas

³

et al. 2021

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This review presents a critical and comprehensive overview of current experimental measurements of complete elastic constant tensors for molecular crystals. For a large fraction of these molecular crystals, detailed comparisons are made with elastic tensors obtained using the corrected small basis set Hartree–Fock method S‐HF‐3c, and these are shown to be competitive with many of those obtained from more sophisticated density functional theory plus dispersion (DFT‐D) approaches. These detailed comparisons between S‐HF‐3c, experimental and DFT‐D computed tensors make use of a novel rotation‐invariant spherical harmonic description of the Young's modulus, and identify outliers among sets of independent experimental results. The result is a curated database of experimental elastic tensors for molecular crystals, which we hope will stimulate more extensive use of elastic tensor information—experimental and computational—in studies aimed at correlating mechanical properties of molecular crystals with their underlying crystal structure.

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“…For example, ISTS measurements have been performed on polished thin slabs 600–800 μm thick for the explosives PETN and RDX, [27] enabling a critical comparison with previous ultrasonic, RUS and Brillouin scattering results, and this comparison is discussed in detail in Section 5.14. Less commonly, elastic tensors have also been obtained from the thermal diffuse scattering of X‐rays, [28–33] and from inelastic neutron scattering [34]…”

Section: Introductionmentioning

confidence: 99%

Quantifying Mechanical Properties of Molecular Crystals: A Critical Overview of Experimental Elastic Tensors

Spackman

¹

,

Grosjean

²

,

Thomas

³

et al. 2021

View full text Add to dashboard Cite

This review presents a critical and comprehensive overview of current experimental measurements of complete elastic constant tensors for molecular crystals. For a large fraction of these molecular crystals, detailed comparisons are made with elastic tensors obtained using the corrected small basis set Hartree–Fock method S‐HF‐3c, and these are shown to be competitive with many of those obtained from more sophisticated density functional theory plus dispersion (DFT‐D) approaches. These detailed comparisons between S‐HF‐3c, experimental and DFT‐D computed tensors make use of a novel rotation‐invariant spherical harmonic description of the Young's modulus, and identify outliers among sets of independent experimental results. The result is a curated database of experimental elastic tensors for molecular crystals, which we hope will stimulate more extensive use of elastic tensor information—experimental and computational—in studies aimed at correlating mechanical properties of molecular crystals with their underlying crystal structure.

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“…where N is the number of unit cells, I 0 the incident beam intensity, Q the total scattering vector, k B the Boltzmann constant, T the temperature, q the momentum transfer, f the atomic scattering factor of ion s with mass m and Debye-Waller factor M and ρ is the density of the material. A detailed explanation of the formalism can be found in [258,244,245,29]. By measuring TDS at two different temperatures, it is possible to isolate the component of the diffuse scattering due to the static disorder, air scattering and fluorescence, as they show a much smaller temperature dependence than TDS.…”

Section: Thermal Diffuse Scatteringmentioning

confidence: 99%

“…(2.48) where C is constrained by the crystal symmetry, and b and g are kept in the vicinity of the individual Bragg reflections [245,29]. A more detailed description on the TDS analysis is beyond the scope of this thesis and can be found in [245,29,159,244,258].…”

Section: Thermal Diffuse Scatteringmentioning

confidence: 99%

“…(2.48) where C is constrained by the crystal symmetry, and b and g are kept in the vicinity of the individual Bragg reflections [245,29]. A more detailed description on the TDS analysis is beyond the scope of this thesis and can be found in [245,29,159,244,258]. In this thesis TDS experiments were performed at the P21.1 beamline at PETRA-III, DESY, Hamburg, Germany (the results of the study are reported in Ch.…”

Section: Thermal Diffuse Scatteringmentioning

confidence: 99%

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Elastic properties of carbonates

Pennacchioni¹

0

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Carbon is an element that controls planetary habitability, and is fundamental for life on Earth. Its behaviour has important consequences for the global climate system, the origin and evolution of life on Earth. While the biosphere and atmosphere’s carbon cycle only accounts for less than 1% of the global carbon budget, hidden reservoirs of deep carbon in the Earth’s interior comprise the predominant storage of carbon on the planet. At the Earth’s surface, 60-70 % of carbon is hosted by carbonate minerals, which are then transported to the Earth’s interior, mainly in the form of sediments, by subduction of the oceanic lithosphere. Subducting plates are subjected to decarbonation, dehydration, and melting with CO2 release via supra-subduction volcanism. Nevertheless, part of the subducted carbonates’ may survive and be further transported to the deep mantle. Direct evidence of the existence of carbonates in the Earth’s interior, possibly reaching down to the lower mantle, comes from the finding of syngenetic inclusions of carbonates in diamonds and mantle xenoliths. The presence of carbonates in the deep Earth has a critical effect on the physical properties of the mantle. Melting and chemical speciation of the mantle are strongly affected by the form of C and carbonate stability. Therefore, the study of the stability and physical properties of carbonates at high pressures and temperatures is fundamental, because understanding the processes involved in the deep carbon cycle helps to improve our picture of the whole mantle. The systematic characterization of the elastic properties of carbonates as a function of their structure and chemical composition is of great importance because it may allow to identify their presence and distribution by seismology. Inverting seismic observations to successfully constrain the chemical composition and mineralogy of the Earth’s interior requires knowledge of the physical properties of all possible Earth’s materials at pressures and temperatures applicable to the Earth’s interior. Up to now, a multitude of studies has focused on the construction of phase diagrams and structural transitions by means of X-ray diffraction and vibrational spectroscopy experiments. Few studies are available on the complete elastic tensor of carbonates, however most of the datasets are not accompanied by an accurate characterization of the samples, which are often solid solutions and the exact chemical composition, density or the details about the experimental methods used are not presented. The aim of this thesis is to study the effect of chemical composition on the elastic properties of carbonates, providing a reliable dataset on the elasticity of the main carbonates. In particular, the elastic properties of crystalline aragonite, CaCO3, and Fe-dolomite, (Ca, Mg, Fe)(CO3)2, with different compositions were studied by Brillouin spectroscopy at ambient conditions. Brillouin spectroscopy was also used to investigate the elastic behaviour of amorphous calcium carbonate samples with different water contents (up to 18 wt%) at high pressures, up to 20 GPa. Furthermore, the importance of cationic substitution on the structure and high pressure behaviour of carbonates was investigated by studying a synthetic CaCO3-SrCO3 solid solution at ambient conditions and at high pressures, up to 10 GPa, by single crystal X-ray diffraction. Finally, the study of the effect of composition on the elastic properties of families of isostructural solids was also extended to a different class of materials, the metal guanidinium formates. The elasticity of a family of perovskite metal organic frameworks, metal guanidinium formates C(NH2)3MII(HCOO)3, with MII =Mn, Zn, Cu, Co, Cd and Ca was investigated by combining Brillouin spectroscopy, resonant ultrasound spectroscopy, density functional theory and thermal diffuse scattering analysis.

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Elastic stiffness coefficients of thiourea from thermal diffuse scattering

Cited by 4 publications

References 33 publications

Quantifying Mechanical Properties of Molecular Crystals: A Critical Overview of Experimental Elastic Tensors

Quantifying Mechanical Properties of Molecular Crystals: A Critical Overview of Experimental Elastic Tensors

Quantifying Mechanical Properties of Molecular Crystals: A Critical Overview of Experimental Elastic Tensors

Elastic properties of carbonates

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