arXiv subjects

Simon R. Hall

Publications and source records attributed to Simon R. Hall.

5 recordsLinked to original sources

arXiv2026

Magnetism and 3D Electron Diffraction Solution of Hydrated Rubidium-Ruthenium Oxide Rb$_2$Ru$_2$O$_7$.H$_2$O

The crystal structure of Rb$_2$Ru$_2$O$_7$.H$_2$O was determined by three-dimensional electron diffraction from the individual crystallites of a solid-state powder product. Rb$_2$Ru$_2$O$_7$.H$_2$O crystallizes in space group \textit{C}2/\textit{c} ($a=7.841(3)$ \AA, $b=12.500(3)$ \AA, $c=8.392(2)$ \AA, $\beta=93.57(4)^\circ$, Z=4). The structure contains infinite chains that run normal to the (101) plane and consist of alternating RuO$_6$ octahedra and square-pyramidal RuO$_5$ units connected via shared O-O edges. Magnetic properties were measured on the bulk powder, showing a diamagnetic baseline from 300 to 60 K with a small Curie tail below 55 K. The magnetic moment, calculated from the 1.8 K isotherm, saturates at $M=4.4\times10^{-3}\,\mu_\mathrm{B}\,\mathrm{Ru}^{-1}$, much less than would be expected for $S=1$ ruthenium. Bond-valence-sum analysis indicates high-valent Ru, and the near-diamagnetic response is consistent with the edge-sharing Ru-Ru motif, where weak direct Ru-Ru overlap yields a local singlet.

cond-mat.mtrl-sci↗

arXiv2023

Explosive Chrysopoeia

Fulminating gold, the first high-explosive compound to be discovered, disintegrates in a mysterious cloud of purple smoke, the nature of which has been speculated upon since its discovery in 1585. In this work, we show that the colour of the smoke is due to the presence of gold nanoparticles.

cond-mat.mtrl-sci↗

arXiv2020

Crystallisation From Volatile Deep Eutectic Solvents

A new class of deep eutectic solvents are presented where one component of the system is inherently volatile, enabling a premeditated, auto-destructive capability which leads inexorably to a series of novel crystal structures. These volatile deep eutectic solvents are easily-formed liquids with a greatly depressed melting point and exhibit all of the physical characteristics of classical deep eutectic solvents, with the exception that the hydrogen-bond donor component is volatile when exposed to the atmosphere at room temperature. We demonstrate the effectiveness of this concept through the exquisite control of pharmaceutical polymorphism, among which is a more efficacious form of acetaminophen, which can be formed spontaneously for the first time at room temperature.

physics.chem-ph↗

arXiv2018

The Effect of Isotropic Pressure on the Electronic Structure and Superatomic Orbitals of Molecular [Ag44(SPhCOOH)30]4-, [Ag44(SPhF2)30]4- & [Ag25(SPhMe2)18]- Nanoclusters

We present the first experimental investigation of the effect of increased isotropic pressure on the superatomic electronic structure of metal nanoclusters in the molecular state. Broad multiband absorbing [Ag44(SPhCOOH)30]4-, [Ag44(SPhF2)30]4- & [Ag25(SPhMe2)18]- nanoclusters were optically examined up to 200 MPa, revealing a reversible change to the superatomic electronic structure. Deviations from the ambient spectra became significant above 50 MPa, revealing both red and blue shifts to spectral features. Comparison of the spectral peaks to calculated electronic transitions indicate that electronic states on the ligand are destabilized and that the splitting of the superatomic orbitals decreases with increasing pressure. These findings highlight that under relatively modest pressure the fundamental superatomic electronic structure of metal nanoclusters can be manipulated, thus the optical and electronic properties of functional materials containing nanoclusters such as in solar cells and photocatalytic devices can be tuned by the application of pressure.

cond-mat.mes-hall↗

arXiv2015

Control of polymorphism in coronene by the application of magnetic fields

Coronene, a polyaromatic hydrocarbon, has been crystallized for the first time in a different polymorph using a crystal growth method that utilizes magnetic fields to access a unit cell configuration that was hitherto unknown. Crystals grown in magnetic field of 1 T are larger, have a different appearance to those grown in zero field and retain their structure in ambient conditions. We identify the new form, beta-coronene, as the most stable at low temperatures. As a result of the new supramolecular configuration we report significantly altered electronic, optical and mechanical properties.

cond-mat.mtrl-sci↗