Colin R. Pulham

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

The discovery of three new polymorphs of methyl behenate highlights the need for clear methodologies for the design of sustainable thermal energy storage materials.

The locations and occupancies of deuterium atoms in molybdenum deuteride were studied using time-of-flight neutron powder diffraction under pressures up to ∼6.2 GPa. We confirmed the P6₃/mmc space group and determined the overstoichiometric deuterium content to give a composition of MoD_1.15, showing that our data are sensitive to deuterium positions and occupancies. In MoD_1.15, the majority of the interstitial deuterium atoms occupy the octahedral sites, and the remainder occupy the tetrahedral sites and exhibit relatively short interatomic distances of 1.49 and 1.90 Å to molybdenum atoms.

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.

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