ORCID Profile
0000-0002-8715-5835
Current Organisation
Science and Technology Facilities Council
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Publisher: Elsevier BV
Date: 12-1999
Publisher: American Chemical Society (ACS)
Date: 31-08-2012
DOI: 10.1021/IC3011184
Abstract: This work describes a comprehensive assignment of the vibrational spectra of the platinum(II) diimine bisthiolate and chloride complexes as a prototype structure for a ersity of Pt(II) diimine chromophores. The dynamics and energy dissipation pathways in excited states of light harvesting molecules relies largely on the coupling between the high frequency and the low frequency modes. As such, the assignment of the vibrational spectrum of the chromophore is of utmost importance, especially in the low-frequency region, below 500 cm(-1), where the key metal-ligand framework modes occur. This region is experimentally difficult to access with infrared spectroscopy and hence frequently remains elusive. However, this region is easily accessible with Raman and inelastic neutron scattering (INS) spectroscopies. Accordingly, a combination of inelastic neutron scattering and Raman spectroscopy with the aid of computational results from periodic-DFT and the mode visualizations, as well as isotopic substitution, allowed for an identification of the modes that contain significant contributions from Pt-Cl, Pt-S, and Pt-N stretch modes. The results also demonstrate that it is not possible to assign transition energies to "pure", localized modes in the low frequency region, as a consequence of the anticipated severe coupling that occurs among the skeletal modes. The use of INS has proved invaluable in identifying and assigning the modes in the lowest frequency region, and overall the results will be of assistance in analyzing the structure of the electronic excited state in the families of chromophores containing a Pt(diimine) core.
Publisher: Royal Society of Chemistry (RSC)
Date: 2004
DOI: 10.1039/B308989D
Publisher: Springer Science and Business Media LLC
Date: 07-02-2019
DOI: 10.1038/S41467-019-08598-Z
Abstract: Pyrochlore systems are ideally suited to the exploration of geometrical frustration in three dimensions, and their rich phenomenology encompasses topological order and fractional excitations. Classical spin ices provide the first context in which it is possible to control emergent magnetic monopoles, and anisotropic exchange leads to even richer behaviour associated with large quantum fluctuations. Whether the magnetic ground state of Yb 2 Ti 2 O 7 is a quantum spin liquid or a ferromagnetic phase induced by a Higgs transition appears to be s le dependent. Here we have determined the role of structural defects on the magnetic ground state via the diffuse scattering of neutrons. We find that oxygen vacancies stabilise the spin liquid phase and the stuffing of Ti sites by Yb suppresses it. S les in which the oxygen vacancies have been eliminated by annealing in oxygen exhibit a transition to a ferromagnetic phase, and this is the true magnetic ground state.
Publisher: AIP Publishing
Date: 04-2023
DOI: 10.1063/5.0147610
Abstract: 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 associated quasi-RUMs. We discuss the role of the bond-bending flexibility within the ScF6 octahedra, and how this enables other phonons to make an additional but ultimately much weaker contribution to negative thermal expansion. These results inform recent discussions on the role of correlated atomic motions in giving rise to negative thermal expansion in ScF3.
Publisher: American Physical Society (APS)
Date: 12-03-2010
Publisher: Springer Science and Business Media LLC
Date: 19-10-2007
Publisher: American Physical Society (APS)
Date: 11-03-2019
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-2018
Abstract: A widely applicable method for accessing phonon dispersions of materials at high spatial resolution is demonstrated.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Keith Refson.