Wyniki wyszukiwania dla: Colin R. Pulham

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artykuł

A Review of the Catalytic Effects of Lead‐Based Ballistic Modifiers on the Combustion Chemistry of Double Base Propellants

Lisette R. Warren, Zixuan Wang, Colin R. Pulham, Carole A. Morrison

Propellants, Explosives, Pyrotechnics > 46 > 1 > 13 - 25

Lead‐based compounds are the current industry‐standard ballistic modifier for double‐base propellants, but there is a pressing need for alternatives as incoming European legislation will soon ban their use. This review article introduces the main concepts and terminologies in the combustion chemistry of double‐base propellants, and critically evaluates the four theories put forward in the literature...

artykuł

A new high‐pressure polymorph of phosphoric acid

Craig L. Bull, Nicholas P. Funnell, Colin R. Pulham, William G. Marshall, więcej

Acta Crystallographica Section B > 73 > 6 > 1068 - 1074

The high‐pressure structural behaviour of phosphoric acid is described. A compression study of the monoclinic phase, using neutron powder diffraction and X‐ray single‐crystal diffraction, shows that it converts to a previously unobserved orthorhombic phase on decompression. Compression of this new phase is reported up to 6.3 GPa. The orthorhombic phase is found to be more efficiently packed, with...

artykuł

Pressure-induced structural changes in Methylamine borane and dimethylamine borane

Petra Á. Szilágyi, Steven Hunter, Carole A. Morrison, Chiu C. Tang, więcej

Journal of Alloys and Compounds > 2017 > 722 > C > 953-961

Methylamine borane and dimethylamine borane have been studied under compression to 3 GPa using Raman spectroscopy and synchrotron powder X-ray diffraction. Both undergo reversible pressure-induced structural changes in this pressure range. The structural changes in the case of methylamine borane may be indicative of a second-order phase transition, taking place between ca. 0.8–1.2 GPa, which does...

rozdział

High-Pressure Studies of Energetic Materials

Colin R. Pulham, David I. A. Millar, Iain D. H. Oswald, William G. Marshall

NATO Science for Peace and Security Series B: Physics and Biophysics > High-Pressure Crystallography > 447-457

High-pressure studies of energetic materials provide valuable information about how these compounds behave under the extreme conditions experienced during detonation. Spectroscopic and diffraction techniques, augmented by computational methods, provide insight into the effects of pressure on intermolecular interactions and phase transitions. Some examples of studies on representative compounds are...

artykuł

Towards an understanding of crystallization from solution. DFT studies of multi-component serotonin crystals

Denis A. Rychkov, Steven Hunter, Viktor Yu. Kovalskii, Alexander A. Lomzov, więcej

Computational and Theoretical Chemistry > 2016 > 1088 > C > 52-61

A potential energy surface (PES) has been calculated for the protonated serotonin (5-HT) molecule in aqueous media. Three pairs of symmetrically equivalent minima were located using fully relaxed optimization at B3LYP/6-31G(d,p) level of theory. Insensitivity to basis set was verified over a range of different functionals and levels of theory. All 9 transition structures were found using the QST3...

artykuł

Combined Experimental and Computational Hydrostatic Compression Study of Crystalline Ammonium Perchlorate

Steven Hunter, Alistair J. Davidson, Carole A. Morrison, Colin R. Pulham, więcej

The Journal of Physical Chemistry C > 2011 > 115 > 38 > 18782 - 18788

artykuł

A New Polymorph of N , N ′-Dimethylurea Characterized by X-ray Diffraction and First-Principles Lattice Dynamics Calculations

David. M. S. Martins, Christopher K. Spanswick, Derek S. Middlemiss, Nasir Abbas, więcej

The Journal of Physical Chemistry A > 2009 > 113 > 20 > 5998 - 6003

artykuł

Temperature- and Pressure-Induced Proton Transfer in the 1:1 Adduct Formed between Squaric Acid and 4,4′-Bipyridine

David M. S. Martins, Derek S. Middlemiss, Colin R. Pulham, Chick C. Wilson, więcej

Journal of the American Chemical Society > 2009 > 131 > 11 > 3884 - 3893

artykuł

In Situ Characterization of Elusive Salt HydratesThe Crystal Structures of the Heptahydrate and Octahydrate of Sodium Sulfate

Iain D. H. Oswald, Andrea Hamilton, Christopher Hall, William G. Marshall, więcej

Journal of the American Chemical Society > 2008 > 130 > 52 > 17795 - 17800

artykuł

Noncovalent Interactions under Extreme Conditions: High-Pressure and Low-Temperature Diffraction Studies of the Isostructural Metal−Organic Networks (4-Chloropyridinium) ₂ [CoX ₄ ] (X = Cl, Br)

Guillermo Mínguez Espallargas, Lee Brammer, David R. Allan, Colin R. Pulham, więcej

Journal of the American Chemical Society > 2008 > 130 > 28 > 9058 - 9071

artykuł

A high-pressure form of sulfuric acid monohydrate as determined by X-ray and neutron diffraction

Francesca P.A. Fabbiani, David R. Allan, Alice Dawson, Duncan J. Francis, więcej

Inorganica Chimica Acta > 2008 > 361 > 2 > 487-494

Two high-pressure polymorphs of sulfuric acid monohydrate (oxonium hydrogensulfate) have been obtained at ambient temperature by crystallisation at high pressure from the liquid at 1.3GPa (form III) and by direct compression of the ambient-pressure form I first to 1.26GPa (form II) and then to 1.72GPa (form III). The structure of form III was solved by single crystal X-ray diffraction and this structure...

artykuł

Is engaging with the public optional?

Colin R. Pulham

Materials Today > 2007 > 10 > 12 > 72

The establishment of public trust and confidence is of critical importance, if science is to continue to receive support.

artykuł

High-Pressure Studies of Pharmaceuticals: An Exploration of the Behavior of Piracetam

Francesca P. A. Fabbiani, David R. Allan, William I. F. David, Alistair J. Davidson, więcej

Crystal Growth & Design > 2007 > 7 > 6 > 1115 - 1124

artykuł

Effect of High Pressure on the Crystal Structures of Polymorphs of Glycine

Alice Dawson, David R. Allan, Scott A. Belmonte, Stewart J. Clark, więcej

Crystal Growth & Design > 2005 > 5 > 4 > 1415 - 1427

artykuł

High-pressure recrystallisation—a route to new polymorphs and solvates of acetamide and parabanic acid

Francesca P.A. Fabbiani, David R. Allan, William G. Marshall, Simon Parsons, więcej

Journal of Crystal Growth > 2005 > 275 > 1-2 > 185-192

Although the application of high pressure to organic compounds may favour thermodynamically the adoption of a new polymorphic form, for compounds with high melting points there is often a substantial kinetic barrier to be overcome before the molecules can rearrange. Hence pressure-induced phase changes are often very slow or may not occur at all. We have overcome this problem by growing single crystals...

artykuł

Some Chemical Properties of Monochlorogallane: Decomposition to Gallium(I) Trichlorogallate(III), Ga ⁺ [GaCl ₃ H] ^- , and Other Reactions

Emma Johnsen, Anthony J. Downs, Michael J. Goode, Timothy M. Greene, więcej

Inorganic Chemistry > 2001 > 40 > 18 > 4755 - 4761

artykuł

Preparation and Properties of Gallaborane, GaBH ₆ : Structure of the Gaseous Molecule H ₂ Ga(μ-H) ₂ BH ₂ As Determined by Vibrational, Electron Diffraction, and ab Initio Studies, and Structure of the Crystalline Solid at 110 K As Determined by X-ray Diffraction ^†

Anthony J. Downs, Tim M. Greene, Emma Johnsen, Paul T. Brain, więcej

Inorganic Chemistry > 2001 > 40 > 14 > 3484 - 3497

artykuł

Methylzinc tetrahydroborate: investigation of the vapour phase by spectroscopic and quantum chemical techniques

Simon Aldridge, Anthony J. Downs, Matthias Hofmann, Colin R. Pulham, więcej

Journal of Molecular Structure > 1998 > 444 > 1-3 > 29-46

Methylzinc tetrahydroborate vapour, as shown by its mass and infrared spectra, consists of an equilibrium mixture of monomeric and dimeric species; the proportion of the dimer increases as the temperature is raised from 243 to 268 K (at pressures < 10 ^- ¹ Torr). Consistent with the results of Density Functional Theory (DFT) calculations, the pattern of infrared bands of the matrix-isolated...

artykuł

The molecular structure of trimethyltantalum dichloride, (CH ₃ ) ₃ TaCl ₂ , as determined by gas electron diffraction

Arne Haaland, Hans Peter Verne, Hans Vidar Volden, Colin R. Pulham

Journal of Molecular Structure > 1996 > 376 > 1-3 Special Issue Spectroscopy and Quantum Chemical Theory Applied to Problems in Molecular Structure > 151-155

The gas electron diffraction data of (CH ₃ ) ₃ TaCl ₂ , recorded with a nozzle temperature of about 25 ^o C, show that the coordination geometry of the metal atom is trigonal bipyramidal with the Cl atoms in axial positions. Least-squares refinements based on a molecular model (hydrogen atoms excluded) of D ₃ _h symmetry yield the bond distances (r _a ...

artykuł

The vibrational spectra of natural and perdeuterated monochlorogallane, H ₂ Ga(μ-Cl) ₂ GaH ₂ , and an empirical harmonic potential function

Colin R. Pulham, Anthony J. Downs, Michael J. Goode, Ian M. Mills

Spectrochimica Acta Part A: Molecular Spectroscopy > 1995 > 51 > 5 > 769-777

The infrared and Raman spectra of monochlorogallane and its fully deuterated isotopomer are recorded and assigned on the basis of the dimeric structures. H ₂ Ga(μ-Cl) ₂ GaH ₂ and D ₂ Ga(μ-Cl) ₂ GaD ₂ , conforming to D ₂ _h symmetry. The observed frequencies are corrected for anharmonicity and fitted to a potential function in which 19 of...

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