C. A. Tulk
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View article: Kirkpatrick-Baez super mirror optics for intense neutron microbeams.
Kirkpatrick-Baez super mirror optics for intense neutron microbeams. Open
High-performance neutron super mirrors in the Kirkpatrick-Baez (KB) geometry can efficiently focus polychromatic neutron beams to small spots. We have recently demonstrated near ideal performance with a prototype system designed to produce…
View article: Spin–Phonon Interactions and Anharmonic Lattice Dynamics in Fe<sub>3</sub>GeTe<sub>2</sub>
Spin–Phonon Interactions and Anharmonic Lattice Dynamics in Fe<sub>3</sub>GeTe<sub>2</sub> Open
Raman scattering is performed on Fe 3 GeTe 2 (FGT) at temperatures from 8 to 300 K and under pressures from the ambient pressure to 9.43 GPa. Temperature‐dependent and pressure‐dependent Raman spectra are reported. The results reveal respe…
View article: Neutron scattering study of polyamorphic THF·17(H<sub>2</sub>O) – toward a generalized picture of amorphous states and structures derived from clathrate hydrates
Neutron scattering study of polyamorphic THF·17(H<sub>2</sub>O) – toward a generalized picture of amorphous states and structures derived from clathrate hydrates Open
Neutron scattering and simulation unveil amorphous clathrate hydrate structures. THF·17(H 2 O) yields three amorphs under high pressure and low temperature, resembling amorphous ice. THF and water's local structure is shaped by guest–host …
View article: Dose calibration of Health Canada's Fixed Point Surveillance system for environmental radiation monitoring in terms of air kerma and H*(10)
Dose calibration of Health Canada's Fixed Point Surveillance system for environmental radiation monitoring in terms of air kerma and H*(10) Open
The environmental radiation exposure in Canada has been monitored since 2002 by Health Canada's Fixed Point Surveillance network. The network consists of over eighty 7.6 cm × 7.6 cm sodium iodide spectrometers, and routinely reports to the…
View article: In situ inelastic neutron scattering of mixed CH4–CO2 hydrates
In situ inelastic neutron scattering of mixed CH4–CO2 hydrates Open
An abundant source of CH4 can be found in natural hydrate deposits. Recent demonstration of CH4 recovery from hydrates via CO2 exchange has revealed the potential as a fuel source that also provides a medium for carbon sequestration. It is…
View article: Exploring High-Pressure Transformations in Low-Z (H2, Ne) Hydrates at Low Temperatures
Exploring High-Pressure Transformations in Low-Z (H2, Ne) Hydrates at Low Temperatures Open
The high pressure structural behavior of H2 and Ne clathrate hydrates with approximate composition H2/Ne·~4H2O and featuring cubic structure II (CS-II) was investigated by neutron powder diffraction using the deuterated analogues at ~95 K.…
View article: Pressure-induced amorphization of noble gas clathrate hydrates
Pressure-induced amorphization of noble gas clathrate hydrates Open
The high-pressure structural behavior of the noble gas (Ng) clathrate hydrates Ar center dot 6.5 H2O and Xe center dot 7.2 H2O featuring cubic structures II and I, respectively, was investigated by neutron powder diffraction (using the deu…
View article: Structural investigation of three distinct amorphous forms of Ar hydrate
Structural investigation of three distinct amorphous forms of Ar hydrate Open
Three amorphous forms of Ar clathrate hydrate (pressure-amorphized, annealed and recovered) were characterized by isotope substitution ( 36 Ar) neutron diffraction and molecular dynamics and their local coordinations analyzed and compared …
View article: Distance-Selected Topochemical Dehydro-Diels–Alder Reaction of 1,4-Diphenylbutadiyne toward Crystalline Graphitic Nanoribbons
Distance-Selected Topochemical Dehydro-Diels–Alder Reaction of 1,4-Diphenylbutadiyne toward Crystalline Graphitic Nanoribbons Open
Solid-state topochemical polymerization (SSTP) is a promising method to construct functional crystalline polymeric materials, but in contrast to various reactions that happen in solution, only very limited types of SSTP reactions are repor…
View article: The crystallization transformations sequence as ice is compressed at low temperature: avoidance of amorphization
The crystallization transformations sequence as ice is compressed at low temperature: avoidance of amorphization Open
The compression of ice I is, as expected, seen to form high density amorphous (HDA) ice when compressed continuously to ~ 1 GPa.However, when ice I is compressed at a slower rate, with breaks between 1 Atm and 1 GPa, the formation of HDA c…
View article: First Experiments: New Science Opportunities at the Spallation Neutron Source Second Target Station (abridged)
First Experiments: New Science Opportunities at the Spallation Neutron Source Second Target Station (abridged) Open
This brochure is an abridged version of a more comprehensive companion report. DOE proposes to build a Second Target Station (STS) at SNS to produce beams of cold neutrons with world-leading peak brightness at a repetition rate of 15 Hz, p…
View article: First Experiments: New Science Opportunities at the Spallation Neutron Source Second Target Station
First Experiments: New Science Opportunities at the Spallation Neutron Source Second Target Station Open
Leadership in materials science underpins future technologies in energy, security, and other applications that drive this nation’s economy. Neutron scattering is among the crucial characterization techniques necessary to ensure a world-lea…
View article: Elucidation of the pressure induced amorphization of tetrahydrofuran clathrate hydrate
Elucidation of the pressure induced amorphization of tetrahydrofuran clathrate hydrate Open
The type II clathrate hydrate (CH) THF·17 H2O (THF = tetrahydrofuran) is known to amorphize on pressurization to ∼1.3 GPa in the temperature range 77–140 K. This seems to be related to the pressure induced amorphization (PIA) of hexagonal …
View article: Structure and disorder in ice VII on the approach to hydrogen-bond symmetrization
Structure and disorder in ice VII on the approach to hydrogen-bond symmetrization Open
We have collected neutron-diffraction data of sufficient quality for structural refinement from deuterated ice VII to over 60 GPa. At these pressures, we are approaching the onset of molecular dissociation where the water molecule should b…
View article: Compression mechanisms of ferroelectric PbTiO<sub>3</sub> via high pressure neutron scattering
Compression mechanisms of ferroelectric PbTiO<sub>3</sub> via high pressure neutron scattering Open
Switchable atomic displacements generate electric dipole moments in ferroelectric materials utilized in many contemporary devices. Lead titanate, a perovskite oxide with formula PbTiO3, has been referred to as a textbook example of a proto…
View article: A suite-level review of the neutron powder diffraction instruments at Oak Ridge National Laboratory
A suite-level review of the neutron powder diffraction instruments at Oak Ridge National Laboratory Open
The suite of neutron powder diffractometers at Oak Ridge National Laboratory (ORNL) utilizes the distinct characteristics of the Spallation Neutron Source and High Flux Isotope Reactor to enable the measurements of powder samples over an u…
View article: Characterization of Crystallographic Structures Using Bragg-Edge Neutron Imaging at the Spallation Neutron Source
Characterization of Crystallographic Structures Using Bragg-Edge Neutron Imaging at the Spallation Neutron Source Open
Over the past decade, wavelength-dependent neutron radiography, also known as Bragg-edge imaging, has been employed as a non-destructive bulk characterization method due to its sensitivity to coherent elastic neutron scattering that is ass…
View article: Emerging challenges in high-pressure neutron scattering
Emerging challenges in high-pressure neutron scattering Open
Neutron scattering, in its multiple forms is one of the chief techniques in the study of the structure of materials.However, owing to its relatively poor scattering cross section, it traditionally required significantly large samples, espe…
View article: Pressure‐Induced Polymerization of Acetylene: Structure‐Directed Stereoselectivity and a Possible Route to Graphane
Pressure‐Induced Polymerization of Acetylene: Structure‐Directed Stereoselectivity and a Possible Route to Graphane Open
Geometric isomerism in polyacetylene is a basic concept in chemistry textbooks. Polymerization to cis‐isomer is kinetically preferred at low temperature, not only in the classic catalytic reaction in solution but also, unexpectedly, in the…
View article: Radiation attenuation by single-crystal diamond windows
Radiation attenuation by single-crystal diamond windows Open
As artificial diamond becomes more cost effective it is likely to see increasing use as a window for sample environment equipment used in diffraction experiments. Such windows are particularly useful as they exhibit exceptional mechanical …
View article: Polymerization of Acetonitrile via a Hydrogen Transfer Reaction from CH<sub>3</sub> to CN under Extreme Conditions
Polymerization of Acetonitrile via a Hydrogen Transfer Reaction from CH<sub>3</sub> to CN under Extreme Conditions Open
Acetonitrile (CH 3 CN) is the simplest and one of the most stable nitriles. Reactions usually occur on the C≡N triple bond, while the C−H bond is very inert and can only be activated by a very strong base or a metal catalyst. It is demonst…
View article: Polymerization of Acetonitrile via a Hydrogen Transfer Reaction from CH<sub>3</sub> to CN under Extreme Conditions
Polymerization of Acetonitrile via a Hydrogen Transfer Reaction from CH<sub>3</sub> to CN under Extreme Conditions Open
Acetonitrile (CH 3 CN) is the simplest and one of the most stable nitriles. Reactions usually occur on the C≡N triple bond, while the C−H bond is very inert and can only be activated by a very strong base or a metal catalyst. It is demonst…
View article: Pressure induced polymerization of acetylide anions in CaC<sub>2</sub> and 10<sup>7</sup> fold enhancement of electrical conductivity
Pressure induced polymerization of acetylide anions in CaC<sub>2</sub> and 10<sup>7</sup> fold enhancement of electrical conductivity Open
Pressure induced polymerization of CaC 2 in the amorphous phase is evidenced for the first time, accompanied by a 10 7 fold enhancement of the electrical conductivity.