Keith Refson
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View article: Impurity Band Formation as a Route to Thermoelectric Power Factor Enhancement in n‐type XNiSn Half‐Heuslers
Impurity Band Formation as a Route to Thermoelectric Power Factor Enhancement in n‐type XNiSn Half‐Heuslers Open
Bandstructure engineering is a key route for thermoelectric performance enhancement. Here, 20–50% Seebeck ( S ) enhancement is reported for XNiCu y Sn half‐Heusler samples based on X = Ti. This novel electronic effect is attributed to the …
View article: Ca3[C2O5]2[CO3] is a pyrocarbonate which can be formed at p, T-conditions prevalent in the Earth’s transition zone
Ca3[C2O5]2[CO3] is a pyrocarbonate which can be formed at p, T-conditions prevalent in the Earth’s transition zone Open
Understanding the fate of subducted carbonates is a prerequisite for the elucidation of the Earth’s deep carbon cycle. Here we show that the concomitant presence of Ca[CO 3 ] with CO 2 in a subducting slab very likely results in the format…
View article: Low energy phonons in single crystal ZrW$_{2}$O$_{8}$
Low energy phonons in single crystal ZrW$_{2}$O$_{8}$ Open
ZrW$_{2}$O$_{8}$ is the prototypical example of a material exhibiting negative thermal expansion (NTE). It is now widely accepted that in ZrW$_{2}$O$_{8}$, and in many other framework materials exhibiting NTE, a collection of low energy ph…
View article: Which phonons contribute most to negative thermal expansion in ScF<b>3</b>?
Which phonons contribute most to negative thermal expansion in ScF<b>3</b>? Open
Using calculations of the phonon distribution in ScF3 across the whole of reciprocal space, we show that the important phonons for the negative thermal expansion in this material are those associated with the rigid unit modes (RUMs) and as…
View article: Nuclear quantum dynamics in Hexamethylenetetramine and its deuterated counterpart: a DFT-augmented neutron study
Nuclear quantum dynamics in Hexamethylenetetramine and its deuterated counterpart: a DFT-augmented neutron study Open
Despite being one of the most thoroughly characterised molecular crystals, hexamethylenetetramine (HMT) and its deuterated counterpart (DHMT), are still not fully understood, especially regarding anharmonic and nuclear quantum effects. In …
View article: The adsorption of nitrobenzene over an alumina-supported palladium catalyst: an infrared spectroscopic study
The adsorption of nitrobenzene over an alumina-supported palladium catalyst: an infrared spectroscopic study Open
The adsorption geometry of nitrobenzene over a 5 wt% Pd/Al 2 O 3 catalyst is investigated by a combination of infrared spectroscopy and DFT calculations.
View article: The contribution of phonons to the thermal expansion of some simple cubic hexaboride structures: SmB<sub>6</sub>, CaB<sub>6</sub>, SrB<sub>6</sub> and BaB<sub>6</sub>
The contribution of phonons to the thermal expansion of some simple cubic hexaboride structures: SmB<sub>6</sub>, CaB<sub>6</sub>, SrB<sub>6</sub> and BaB<sub>6</sub> Open
We have performed first-principles calculations of the structure and lattice dynamics in the metal hexaborides SmB 6 , CaB 6 , SrB 6 and BaB 6 using Density Functional Theory in an attempt to understand the negative thermal expansion in th…
View article: Phonon mechanism for the negative thermal expansion of zirconium tungstate, ZrW<sub>2</sub>O<sub>8</sub>
Phonon mechanism for the negative thermal expansion of zirconium tungstate, ZrW<sub>2</sub>O<sub>8</sub> Open
ZrW 2 O 8 is a famous material showing negative thermal expansion (NTE). Phonon calculations matched to flexibility models show that the NTE arises from many phonons rather than a single mechanism, with flexibility from bending of the ZrO …
View article: Unique features of the structural phase transition in acetylene showing simultaneous characteristics of reconstructive, displacive and order–disorder
Unique features of the structural phase transition in acetylene showing simultaneous characteristics of reconstructive, displacive and order–disorder Open
We have studied the two phases of the molecular crystal acetylene, C 2 H 2 , using calculations of the lattice dynamics by Density Functional Theory methods.
View article: <i>Euphonic</i>: inelastic neutron scattering simulations from force constants and visualization tools for phonon properties
<i>Euphonic</i>: inelastic neutron scattering simulations from force constants and visualization tools for phonon properties Open
Interpretation of vibrational inelastic neutron scattering spectra of complex systems is frequently reliant on accompanying simulations from theoretical models. Ab initio codes can routinely generate force constants, but additional steps a…
View article: New Insights on the Electronic-Structural Interplay in LaPdSb and CePdSb Intermetallic Compounds
New Insights on the Electronic-Structural Interplay in LaPdSb and CePdSb Intermetallic Compounds Open
Multifunctional physical properties are usually a consequence of a rich electronic-structural interplay. To advance our understanding in this direction, we reinvestigate the structural properties of the LaPdSb and CePdSb intermetallic comp…
View article: Euphonic: inelastic neutron scattering simulations from force constants and visualisation tools for phonon properties
Euphonic: inelastic neutron scattering simulations from force constants and visualisation tools for phonon properties Open
Interpretation of vibrational inelastic neutron scattering spectra of complex systems is frequently reliant on accompanying simulations from theoretical models. Ab-initio codes can routinely generate force constants, but additional steps a…
View article: Electronic, Structural, and Mechanical Properties of SiO2 Glass at High Pressure Inferred from its Refractive Index
Electronic, Structural, and Mechanical Properties of SiO2 Glass at High Pressure Inferred from its Refractive Index Open
We report the first direct measurements of the refractive index of silica glass up to 145 GPa that allowed quantifying its density, bulk modulus, Lorenz-Lorentz polarizability, and band gap. These properties show two major anomalies at ∼10…
View article: CSD 2030955: Experimental Crystal Structure Determination
CSD 2030955: Experimental Crystal Structure Determination Open
An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely availabl…
View article: Pressure-induced Pb–Pb bonding and phase transition in Pb<sub>2</sub>SnO<sub>4</sub>
Pressure-induced Pb–Pb bonding and phase transition in Pb<sub>2</sub>SnO<sub>4</sub> Open
High-pressure single-crystal to 20 GPa and powder diffraction measurements to 50 GPa, show that the structure of Pb 2 SnO 4 strongly distorts on compression with an elongation of one axis. A structural phase transition occurs between 10 GP…
View article: Phase stabilities of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>MgCO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>MgCO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>-II studied by Raman spectroscopy, x-ray diffraction, and density functional theory calculations
Phase stabilities ofand-II studied by Raman spectroscopy, x-ray diffraction, and density functional theory calculations Open
Carbonates are the major hosts of carbon on Earth's surface and their fate during subduction needs to be known to understand the deep carbon cycle. Magnesite (${\mathrm{MgCO}}_{3}$) is thought to be an important phase participating in deep…
View article: Stabilities of MgCO<sub>3</sub> Polymorphs up to 150 GPa
Stabilities of MgCO<sub>3</sub> Polymorphs up to 150 GPa Open
View article: Theory of momentum-resolved phonon spectroscopy in the electron microscope
Theory of momentum-resolved phonon spectroscopy in the electron microscope Open
We provide a theoretical framework for the prediction and interpretation of momentum-dependent phonon spectra due to coherent inelastic scattering of electrons. We complete the approach with first-principles lattice dynamics using periodic…
View article: Role of defects in determining the magnetic ground state of ytterbium titanate.
Role of defects in determining the magnetic ground state of ytterbium titanate. Open
View article: Suppression of thermal conductivity without impeding electron mobility in n-type XNiSn half-Heusler thermoelectrics
Suppression of thermal conductivity without impeding electron mobility in n-type XNiSn half-Heusler thermoelectrics Open
Addition of Cu to XNiSn half-Heuslers improves homogeneity and reduces thermal conductivity without affecting electron mobility.
View article: Kagome modes, a new route to ultralow thermal conductivity?
Kagome modes, a new route to ultralow thermal conductivity? Open
From next generation gas turbines to scavenging waste heat from car exhausts, finding new materials with ultra-low thermal conductivity ($κ$) has the potential to lead to large gains in device efficiency. Crystal structures with inherently…
View article: Many-body renormalization of forces in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>f</mml:mi></mml:math>-electron materials
Many-body renormalization of forces in -electron materials Open
We present the implementation of dynamical mean-field theory (DMFT) in the CASTEP ab initio code.
\nWe explain in detail the theoretical framework for DFT+DMFT and we demonstrate our implementation for
\nthree strongly-correlated systems w…
View article: Nanoscale momentum-resolved vibrational spectroscopy
Nanoscale momentum-resolved vibrational spectroscopy Open
A widely applicable method for accessing phonon dispersions of materials at high spatial resolution is demonstrated.
View article: Many-body renormalisation of forces in f-materials
Many-body renormalisation of forces in f-materials Open
We present the implementation of Dynamical Mean-Field Theory (DMFT) in the CASTEP ab-initio code. We explain in detail the theoretical framework for DFT+DMFT and we benchmark our implementation on two strongly-correlated systems with $f$-s…
View article: Diffusion mechanism in the sodium-ion battery material sodium cobaltate
Diffusion mechanism in the sodium-ion battery material sodium cobaltate Open
View article: Effect of Basicity on the Hydrolysis of the Bi(III) Aqua Ion in Solution: An Ab Initio Molecular Dynamics Study
Effect of Basicity on the Hydrolysis of the Bi(III) Aqua Ion in Solution: An Ab Initio Molecular Dynamics Study Open
Hydrolysis of the Bi(III) aqua ion under a range of solution conditions has been studied by means of ab initio molecular dynamics simulations. While the Bi(III) aqua ion is stable in pure water, there is an increasing degree of hydrolysis …
View article: Self-interaction free local exchange potentials applied to metallic systems
Self-interaction free local exchange potentials applied to metallic systems Open
We extend the formalism of local exchange methods to calculate and investigate the electronic structure of metals. It is well-known that the Hartree-Fock method when applied to metals shows unphysical behaviour, however the accurate treatm…
View article: Topological triplon modes and bound states in a Shastry–Sutherland magnet
Topological triplon modes and bound states in a Shastry–Sutherland magnet Open
View article: Multiband One-Dimensional Electronic Structure and Spectroscopic Signature of Tomonaga-Luttinger Liquid Behavior in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">K</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>Cr</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>As</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:mrow></mml:math>
Multiband One-Dimensional Electronic Structure and Spectroscopic Signature of Tomonaga-Luttinger Liquid Behavior in Open
We present angle-resolved photoemission spectroscopy measurements of the quasi-one-dimensional superconductor K_{2}Cr_{3}As_{3}. We find that the Fermi surface contains two Fermi surface sheets, with linearly dispersing bands not displayin…
View article: Tutorial Dataset Of Mdanse 2016 Workshop
Tutorial Dataset Of Mdanse 2016 Workshop Open
This dataset was distributed to delegates attending MDANSE (Molecular (and Lattice) Dynamics to Analyse Neutron Scattering Experiments) 2016 workshop, held at Abingdon, Oxfordshire, United Kingdom during 10-12 November, 2016. More informat…