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result(s) for
"Cottrell, Stephen"
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Mixed-valence hydrides at FeFe-hydrogenase active site mimics
The number of methods to study transient paramagnetic hydrides at organometallic centres is extremely limited. The reactivity of 2Fe2S centres with protons to produce both diamagnetic and paramagnetic systems is of central interest in developing novel catalysts for hydrogen production, inspired by the [FeFe]-hydrogenase enzymes. Here, we show how a combination of spectroscopic and electrochemical techniques is allowing access to detail of the reactivity of key species on these pathways. Electron paramagnetic resonance and infra-red spectroelectrochemical approaches have been used to observe the reduction of pre-generated diamagnetic hydrides. In contrast, avoided level crossing muon spin resonance (ALC-µSR) has been used to form the open-shell species directly and to examine the formation of short-lived intermediates in the reaction process. The combination of these techniques suggests the involvement of terminal hydrides or CO-protonation states on the pathway to the isolable bridging hydride products.
Journal Article
Professional music-making in London : ethnography and experience
\"Professional Music-Making in London is a study that examines the lives and work of Western art musicians from an ethnographic perspective. Drawing in part on his own professional experience, Stephen Cottrell considers to what extent musicians in Western society conform to Alan Merriam's paradigmatic assessment of them as having low status yet high respect, as well as being given an unusual degree of licence to deviate from convention. The book draws on a wide variety of approaches from scholars elsewhere: from ethnomusicologists such as Bruno Nettl and Henry Kingsbury, performance theorists such as Richard Schechner and Victor Turner, as well as psychologists such as Sigmund Freud and Melanie Klein.\"
Many-body quantum muon effects and quadrupolar coupling in solids
Strong quantum zero-point motion (ZPM) of light nuclei and other particles is a crucial aspect of many state-of-the-art quantum materials. However, it has only recently begun to be explored from an ab initio perspective, through several competing approximations. Here we develop a unified description of muon and light nucleus ZPM and establish the regimes of anharmonicity and positional quantum entanglement where different approximation schemes apply. Via density functional theory and path-integral molecular dynamics simulations we demonstrate that in solid nitrogen,
α
–N
2
, muon ZPM is both strongly anharmonic and many-body in character, with the muon forming an extended electric-dipole polaron around a central, quantum-entangled [N
2
–
μ
–N
2
]
+
complex. By combining this quantitative description of quantum muon ZPM with precision muon quadrupolar level-crossing resonance experiments, we independently determine the static
14
N nuclear quadrupolar coupling constant of pristine
α
–N
2
to be –5.36(2) MHz, a significant improvement in accuracy over the previously-accepted value of –5.39(5) MHz, and a validation of our unified description of light-particle ZPM.
Quantum entanglement and uncertainty in the positions of light nuclei and implanted particles can crucially impact our understanding of advanced materials. This paper develops a unified theoretical description of these effects and applies it to muon spectroscopy measurements of a material constant to significantly improve their accuracy.
Journal Article
Quantum spin-liquid states in an organic magnetic layer and molecular rotor hybrid
The exotic properties of quantum spin liquids (QSLs) have continually been of interest since Anderson’s 1973 ground-breaking idea. Geometrical frustration, quantum fluctuations, and low dimensionality are the most often evoked material’s characteristics that favor the long-range fluctuating spin state without freezing into an ordered magnet or a spin glass at low temperatures. Among the few known QSL candidates, organic crystals have the advantage of having rich chemistry capable of finely tuning their microscopic parameters. Here, we demonstrate the emergence of a QSL state in
[
EDT-TTF-CONH
2
]
2
+
[
BABCO
-
]
(EDT-BCO), where the EDT molecules with spin-1/2 on a triangular lattice form layers which are separated by a sublattice of BCO molecular rotors. By several magnetic measurements, we show that the subtle random potential of frozen BCO Brownian rotors suppresses magnetic order down to the lowest temperatures. Our study identifies the relevance of disorder in the stabilization of QSLs.
Journal Article
Music, Dance, Anthropology
The performance of music and dance is always about more than just the performance of music and dance, as this volume consistently shows. Its essays argue for importance of the work of ethnomusicologists and ethnochoreologists, illuminating core anthropological concepts such as embodied knowledge, citizenship, ritual practices, and the construction of individual and group identities via a range of methodologies, from consideration of soundscapes to ethnographic filmmaking.
eBook
Magnetism and ion diffusion in honeycomb layered oxide K2Ni2TeO6
In the quest for developing novel and efficient batteries, a great interest has been raised for sustainable K-based honeycomb layer oxide materials, both for their application in energy devices as well as for their fundamental material properties. A key issue in the realization of efficient batteries based on such compounds, is to understand the K-ion diffusion mechanism. However, investigation of potassium-ion (K
+
) dynamics in materials using e.g. NMR and related techniques has so far been very challenging, due to its inherently weak nuclear magnetic moment, in contrast to other alkali ions such as lithium and sodium. Spin-polarised muons, having a high gyromagnetic ratio, make the muon spin rotation and relaxation (
μ
+
SR) technique ideal for probing ions dynamics in these types of energy materials. Here we present a study of the low-temperature magnetic properties as well as K
+
dynamics in honeycomb layered oxide material
K
2
Ni
2
TeO
6
using mainly the
μ
+
SR technique. Our low-temperature
μ
+
SR results together with complementary magnetic susceptibility measurements find an antiferromagnetic transition at
T
N
≈
27
K. Further
μ
+
SR studies performed at higher temperatures reveal that potassium ions (K
+
) become mobile above 200 K and the activation energy for the diffusion process is obtained as
E
a
=
121
(
13
)
meV. This is the first time that K
+
dynamics in potassium-based battery materials has been measured using
μ
+
SR. Assisted by high-resolution neutron diffraction, the temperature dependence of the K-ion self diffusion constant is also extracted. Finally our results also reveal that K-ion diffusion occurs predominantly at the surface of the powder particles. This opens future possibilities for potentially improving ion diffusion as well as K-ion battery device performance using nano-structuring and surface coatings of the particles.
Journal Article
Correction to: Hybrid Silicon Nanostructures with Conductive Ligands and Their Microscopic Conductivity
Reviewing the results presented in Fig. 4(a) and (b) of this study together with the text discussing this figure.
Journal Article
Lithiation‐Driven LiCrSe2 Shell Growth on Metallic CrSe2 Core Governs the Plateau–Slope Behavior
The growing demand for high‐performance lithium‐ion batteries necessitates the development of cathode materials that combine high capacity, structural stability, and rapid charge–discharge capability. First‐principles calculations predict that layered CrSe2 possesses a robust framework capable of accommodating one Li+ per formula unit while intrinsically supporting fast Li‐ion diffusion. Muon spin rotation (µ+SR) measurements validate this prediction, revealing fast Li+ diffusion in pre‐lithiated CrSe2. Consistent with these findings, electrochemical testing demonstrates a reversible capacity of 125.3 mAh g−1 at 0.1 C, approaching the theoretical value of 127.7 mAh g−1, with stable cycling and good rate capability. In operando X‐ray diffraction and electrochemical impedance spectroscopy further reveal a reversible topotactic transition and a lithiation‐driven core‐shell evolution during cycling. These results show that lithiation‐induced conductivity changes govern the electrochemical behavior of CrSe2, highlighting its potential as a high‐performance cathode for LIBs. This study provides new insight into intercalation processes in layered transition‐metal chalcogenides and informs the design of fast‐charging electrodes. Layered CrSe2 is investigated as a lithium‐ion battery cathode combining fast Li+ diffusion and structural reversibility. Calculations and experiments reveal a single topotactic intercalation process with a characteristic plateau–slope profile governed by lithiation‐induced conductivity changes. A core‐shell lithiation evolution underpins its high‐rate capability and cycling stability.
Journal Article
Hybrid Silicon Nanostructures with Conductive Ligands and Their Microscopic Conductivity
Silicon nanoparticles (SiNPs) functionalized with conjugated molecules are a promising potential pathway for generating an alternative category of thermoelectric materials. While the thermoelectric performance of materials based on phenylacetylene-capped SiNPs has been proven, their low conductivity is still a problem for their general application. A muon study of phenylacetylene-capped SiNPs was recently carried out using the HIFI spectrometer at the Rutherford Appleton Laboratory, measuring the avoided level-crossing spectra as a function of temperature. The results show a reduction in the measured line width of the resonance above room temperature, suggesting an activated behaviour for this system. This study shows that the muon study could be a powerful method for investigating microscopic conductivity of hybrid thermoelectric materials.
Journal Article