arXiv subjects

Ines E. Collings

Publications and source records attributed to Ines E. Collings.

4 recordsLinked to original sources

arXiv2021

Lower pressure phases and metastable states of superconducting photo-induced carbonaceous sulfur hydride

Room-temperature superconductivity was recently discovered in carbonaceous sulfur hydride (C-S-H) close to 3\,Mbar. We report significant differences in the superconducting response of C-S-H, with a maximum $T_{C}$ of 191(1)\,K, below a 1\,Mbar. Variations in intensity of the C-H Raman modes reveal carbon content can vary between crystals synthesized with the same photo-induced method. Synchrotron single crystal x-ray diffraction identifies polymorphism with increasing degrees of covalency. These unique metastable states are highly sensitive to thermodynamic pathways.

cond-mat.supr-con↗

arXiv2020

Persistent spin dynamics in the pressurized spin-liquid candidate YbMgGaO$_4$

Single-crystal x-ray diffraction, density-functional band-structure calculations, and muon spin relaxation ($μ$SR) are used to probe pressure evolution of the triangular spin-liquid candidate YbMgGaO$_4$. The rhombohedral crystal structure is retained up to at least 10 GPa and shows a nearly uniform compression along both in-plane and out-of-plane directions, whereas local distortions caused by the random distribution of Mg$^{2+}$ and Ga$^{3+}$ remain mostly unchanged. The $μ$SR data confirm persistent spin dynamics up to 2.6 GPa and down to 250 mK with no change in the muon relaxation rate. Longitudinal-field $μ$SR reveals power-law behavior of the spin-spin autocorrelation function, both at ambient pressure and upon compression.

cond-mat.str-el↗

arXiv2015

Compositional dependence of anomalous thermal expansion in perovskite-like ABX3 formates

The compositional dependence of thermal expansion behaviour in 19 different perovskite-like metal-organic frameworks (MOFs) of composition [AI][MII(HCOO)3] (A = alkylammonium cation; M = octahedrally-coordinated divalent metal) is studied using variable-temperature X-ray powder diffraction measurements. While all systems show essentially the same type of thermomechanical response-irrespective of their particular structural details-the magnitude of this response is shown to be a function of AI and MII cation radii, as well as the molecular anisotropy of AI. Flexibility is maximised for large MII and small AI, while the shape of AI has implications for the direction of framework hingeing.

cond-mat.mtrl-sci↗

arXiv2011

Static disorder and local structure in zinc(II) isonicotinate, a quartzlike metal-organic framework

Using a combination of Rietveld and RMC refinement of neutron total scattering data, we find that the 10 K structure of zinc(II) isonicotinate shows strong evidence of static disorder. This disorder takes the form of transverse displacements of the isonicotinate ligand and results in elongated atomic displacement parameters and dampened oscillations of the experimental G(r). We analyse the RMC configurations using an approach derived from geometric algebra. Complications regarding the inclusion of hydrogenous guest molecules within the pore structure are discussed. This study highlights the way in which structural flexibility can give rise to multiple low-energy ground states in MOF-type materials.

cond-mat.mtrl-sci↗