Thermoelastic properties of deuterated melamine, C3N6D6, between 4.2–320 K at 5 kPa and between 0.1–5.0 GPa at 295 K from neutron powder diffraction and DFT calculations

Fortes, A. Dominic; Funnell, Nicholas P.; Bull, Craig L.

doi:10.1080/08957959.2019.1578879

Cited by 3 publications

(2 citation statements)

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“…It assumes a higher value if additional intermolecular interactions such as hydrogen bonding are present, e.g. the values for hydroquinone-formic acid clathrate, melamine and l-alanine are 13.6 (4) GPa (Eikeland et al, 2016), 12.0 (5) GPa (Fortes et al, 2019) and 13.4 (7) GPa (Funnell et al, 2010), respectively. Materials characterized by a mixture of dispersion and weaker hydrogen bonds have correspondingly lower bulk moduli, e.g.…”

Section: Tablementioning

confidence: 99%

High-pressure polymorphism in pyridine

Giordano

Beavers

Campbell

et al. 2020

IUCrJ

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Single crystals of the high-pressure phases II and III of pyridine have been obtained by in situ crystallization at 1.09 and 1.69 GPa, revealing the crystal structure of phase III for the first time using X-ray diffraction. Phase II crystallizes in P212121 with Z′ = 1 and phase III in P41212 with Z′ = ½. Neutron powder diffraction experiments using pyridine-d5 establish approximate equations of state of both phases. The space group and unit-cell dimensions of phase III are similar to the structures of other simple compounds with C 2v molecular symmetry, and the phase becomes stable at high pressure because it is topologically close-packed, resulting in a lower molar volume than the topologically body-centred cubic phase II. Phases II and III have been observed previously by Raman spectroscopy, but have been mis-identified or inconsistently named. Raman spectra collected on the same samples as used in the X-ray experiments establish the vibrational characteristics of both phases unambiguously. The pyridine molecules interact in both phases through CH...π and CH...N interactions. The nature of individual contacts is preserved through the phase transition between phases III and II, which occurs on decompression. A combination of rigid-body symmetry mode analysis and density functional theory calculations enables the soft vibrational lattice mode which governs the transformation to be identified.

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Section: Tablementioning

confidence: 99%

High-pressure polymorphism in pyridine

Giordano

Beavers

Campbell

et al. 2020

IUCrJ

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“…Flexible intramolecular torsion angles can provide an additional mechanism for compression, as seen in the P and OP polymorphs of the prodigiously polymorphic compound ‘ROY’ (5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile), for which K 0 = 6.0(7) and 4.3(3) GPa, respectively [27,28]. It assumes a higher value if additional intermolecular interactions such as H−bonding is present, e.g., the value for hydroquinone-formic acid clathrate is K 0 = 13.6(4) GPa [29], and that of melamine is 12.0(5) [30]. Materials characterised by a mixture of dispersion and weaker H-bonds and have correspondingly lower bulk moduli, e.g., aniline (phase II) is 5.4(2) [31].…”

Section: Resultsmentioning

confidence: 99%

The Effect of Pressure on Halogen Bonding in 4-Iodobenzonitrile

et al. 2019

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The crystal structure of 4-iodobenzonitrile, which is monoclinic (space group I2/a) under ambient conditions, contains chains of molecules linked through C≡N···I halogen-bonds. The chains interact through CH···I, CH···N and π-stacking contacts. The crystal structure remains in the same phase up to 5.0 GPa, the b axis compressing by 3.3%, and the a and c axes by 12.3 and 10.9 %. Since the chains are exactly aligned with the crystallographic b axis these data characterise the compressibility of the I···N interaction relative to the inter-chain interactions, and indicate that the halogen bond is the most robust intermolecular interaction in the structure, shortening from 3.168(4) at ambient pressure to 2.840(1) Å at 5.0 GPa. The π∙∙∙π contacts are most sensitive to pressure, and in one case the perpendicular stacking distance shortens from 3.6420(8) to 3.139(4) Å. Packing energy calculations (PIXEL) indicate that the π∙∙∙π interactions have been distorted into a destabilising region of their potentials at 5.0 GPa. The structure undergoes a transition to a triclinic ( P 1 ¯ ) phase at 5.5 GPa. Over the course of the transition, the initially colourless and transparent crystal darkens on account of formation of microscopic cracks. The resistance drops by 10% and the optical transmittance drops by almost two orders of magnitude. The I···N bond increases in length to 2.928(10) Å and become less linear [<C−I∙∙∙N = 166.2(5)°]; the energy stabilises by 2.5 kJ mol−1 and the mixed C-I/I..N stretching frequency observed by Raman spectroscopy increases from 249 to 252 cm−1. The driving force of the transition is shown to be relief of strain built-up in the π∙∙∙π interactions rather than minimisation of the molar volume. The triclinic phase persists up to 8.1 GPa.

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Non-invasive detection of hazardous materials with a thermal-to-epithermal neutron station: a feasibility study towards practical application

Silarski,

Dziedzic-Kocurek,

Drużbicki

et al. 2024

Sci Rep

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The growing scale of the devastation that even a single terrorist attack can cause requires more effective methods for the detection of hazardous materials. In particular, there are no solutions for effectively monitoring threats at sea, both for the off-shore infrastructure and ports. Currently, state-of-the-art detection methods determine the density distribution and the shapes of tested subjects but only allow for a limited degree of substance identification. This work aims to present a feasibility study of the possible usage of several methods available on the thermal-to-epithermal neutron station, VESUVIO, at the ISIS neutron and muon spallation source, UK, for the detection of hazardous materials. To this end, we present the results of a series of experiments performed concurrently employing neutron transmission and Compton scattering using melamine, a commonly used explosive surrogate, in order to determine its signal characteristics and limits of detection and quantitation. The experiments are supported by first-principles modelling, providing detailed scrutiny of the material structure and the nuclear dynamics behind the neutron scattering observables.

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Thermoelastic properties of deuterated melamine, C₃N₆D₆, between 4.2–320 K at 5 kPa and between 0.1–5.0 GPa at 295 K from neutron powder diffraction and DFT calculations

Abstract: Thermoelastic properties of deuterated melamine, C 3 N 6 D 6 , between 4.2-320 K at 5 kPa and between 0.1-5.0 GPa at 295 K from neutron powder diffraction and DFT calculations.

Cited by 3 publications

References 52 publications

High-pressure polymorphism in pyridine

High-pressure polymorphism in pyridine

The Effect of Pressure on Halogen Bonding in 4-Iodobenzonitrile

Non-invasive detection of hazardous materials with a thermal-to-epithermal neutron station: a feasibility study towards practical application

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