Carole A. Morrison

New multicomponent salts of ADN with reduced hygroscopicity and improved handling properties produced by mechanochemistry and spray drying.

Simultaneous imaging and diffraction probes real-time precipitation mechanism for selective metal recovery process.

We report a spectroscopic approach for rapid, small-scale, non-destructive testing of energetic material impact sensitivity.

Machine learning models have been developed to rationalise correlations between molecular structure and sensitivity to initiation by mechanical impact for a data set of 485 energetic molecules.

We present a high-throughput data-driven workflow to identify potential heterogeneous nucleating agents from structural databases for phase change materials, such as ice. Our model evaluates the fit between ice-Ih and nucleator docked slabs, considering Miller index planes up to (3,3,3), thus addressing some of the structural complexities in nucleation by examining crystal morphology features. Bulk water immersion experiments on a set of ten known nucleators set a delineating temperature to distinguish between good and poor nucleation behaviour, which helped derive numerical tolerance limits to allow reliable differentiation on the basis of the number of predicted matching interface models. We then used our algorithm to screen 3,500 simple metal oxides and halides taken from the Inorganic Chemistry Structural Database (ICSD), and show that just 7% of the former and 3% of the latter were predicted to nucleate ice on the basis of geometric slab matching. Subsequent experimental testing of 22 compounds suggested a 64% correct prediction rate, and identified four new ice nucleators (CeO2, WO3, Bi2O3, Ti2O3). Inspired by the ice-nucleating efficiency of copper oxides, we also tested copper tubing with local tap water, and observed sub-cooling suppression, most likely due to copper oxide buildup. Although based on a simple geometric interface matching model, this approach offers an efficient route to screen for heterogeneous nucleating agents.

We present an improved fiber diffraction pattern and interpretation for nitrocellulose, obtained using state-of-the-art facilities available at Diamond Light Source. Beamlines I24 and VMXm permitted unprecedented data collection for delicate nitrated ramie plant fibers that are highly susceptible to radiation damage, allowing correction of historical misassignments of crystal system and unit-cell parameters. We reassign the previously labeled monoclinic or orthorhombic unitcell to a new low-symmetry triclinic unit cell (a = 9.10, b = 8.62, c = 25.80 ˚A, α = 108, β = 116, and γ = 107◦). Containing a single polymer chain, our structure is closely related to the nitrated analogue of the Iα polymorph of cellulose. Model building indicates that the most feasible polymer geometry commensurate with the given c-axis and density measurements (1.78 g cm−3) is the 52 righthanded helix first proposed in 1978. Molecular dynamics simulations performed on a 3 x 3 x 1 supercell representation confirm the helix structure is stable and 1generates a sterically sound side-chain conformation distribution. The simulated diffraction pattern aligns well with the experimental pattern, giving confidence that the correct unit-cell parameters for this polymorph have now been obtained.

The ring-opening polymerisation (ROP) of lactide (LA) is an attractive route to produce aliphatic polyesters, with bimetallic catalysts displaying some of the highest catalyst activities to date. While a range of heterometallic catalysts have been reported to outperform their homometallic analogues, the origins of cooperativity are not always well understood. Previous studies indicate that the reaction pathways may differ for different metal heterocombinations, especially when an alkali metal is combined with zinc or aluminium. Here, a series of homo- and hetero-metallic complexes combining Li with Al, Zn or In, supported by an asymmetric methyl-ester substituted salen ligand (H₂L), have been synthesised and characterised by single-crystal X-ray diffraction, to probe potential differences. The heterobimetallic LLiZnCl, LLiAlCl₂, and LLiInCl₂ complexes were all active for rac-LA ROP in the presence of an epoxide initiator, with LLiInCl₂ offering the most efficient polymerisation while homobimetallic LLi₂ was inactive. Investigations into the roles of the different metals through X-ray diffraction and DFT structural studies suggest that oxophilicity, Lewis acidity, and electronegativity difference between the two metals all play a role, with the high oxophilicity and Lewis acidity of Al overriding the “ate” pathway.

Bimolecular reactions are ubiquitous in chemistry, but it is exceptionally difficult to resolve the motion of atoms for such processes on the ultrafast time scales that the breaking and creation of chemical bonds occur. Detecting small changes in atom positions requires high temporal and spatial resolution and reliable signal-to-noise characteristics. Here, we have exploited solid-state alignment to track a photoinduced bimolecular disproportionation reaction that transforms two pairs of adjacent triiodide anions (I₃^-) into the metastable tetraiodide molecule and the diiodide fragment. We use ultrafast electron diffraction and dynamical structure refinement, where the atomic displacements are directly reconstructed from the diffraction data with plausible restraints on the atomic trajectories starting from the known ground-state structure. The excited-state structures are supported by theoretical calculations in the solid state and the reaction courses show clear site dependence on the ultrafast time scale. Our results provide a close-up view of the atomic motions involved in this classic reaction in real time, from bond elongation to breaking at the parent ion, to collision and subsequent bond formation of the liberated I atom with the neighboring I₃^-, all within a picosecond.

Bimolecular reactions are ubiquitous in chemistry, but it is exceptionally difficult to resolve the motion of atoms for such processes on the ultrafast timescales that the breaking and creation of chemical bonds occur. Detecting small changes in atom positions requires high temporal and spatial resolution and reliable signal-to-noise characteristics. Here, we have exploited solid-state alignment to track a photoinduced bimolecular disproportionation reaction that transforms two pairs of adjacent triiodide anions into the metastable tetraiodide molecule and the diiodide fragment. We use ultrafast electron diffraction and dynamic structure refinement, where the atomic displacements are directly reconstructed from the diffraction data with plausible restraints on the atomic trajectories starting from the known ground-state structure. The excited-state structures are supported by theoretical calculations in the solid state and the reaction courses show clear site dependence on the ultrafast timescale. Our results provide a close-up view of the atomic motions involved in this classic reaction in real time, from bond elongation to breaking at the parent ion, to collision and subsequent bond formation of the liberated I atom with the neighbouring triiodide, all within a picosecond.

Vibrational up-pumping model predicts the mechanically-induced impact sensitivities of 33 molecular energetic crystals.