arXiv subjects

Camilla Di Mino

Publications and source records attributed to Camilla Di Mino.

3 recordsLinked to original sources

arXiv2026

Crystallization of pristine cubic ice from liquid at ambient pressure

The phase diagram of frozen water is famously rich: to date, over twenty crystalline polymorphs have been identified. Of the low-pressure 'ice I' family, hexagonal (Ih) is the principal form on Earth, while cubic (Ic) is much more elusive. Fundamental questions remain open as to whether cubic ice Ic can form directly from the liquid state, its thermodynamic stability and natural occurrence. Here we show that pristine cubic ice Ic can be formed at atmospheric pressure simply by cooling an aqueous solution confined within mesoporous silica. Using primarily neutron scattering, we show unambiguously that under these conditions, cubic ice Ic forms reproducibly and is the only thermodynamically stable crystalline phase of water. The discovery that cubic ice Ic is directly accessible from the liquid state, and stable at atmospheric pressure, strongly suggests that this polymorph plays a much more significant role in natural and synthetic processes than previously thought.

cond-mat.mtrl-sci↗

arXiv2022

Cooperative O-H$\cdotsπ$ and C-H$\cdots$O Hydrogen Bonding in Benzene-Methanol Solution: Strong Structures from Weak Interactions

Weak hydrogen bonds, such as O-H$\cdotsπ$ and C-H$\cdots$O, are pivotal in a wide range of important natural and industrial processes including biochemical assembly, molecular recognition, and chemical selectivity. In this study we use neutron diffraction in conjunction with comprehensive H/D isotopic substitution to obtain a detailed spatial and orientational picture of the structure in benzene-methanol solution. This system provides us with a prototypical situation where the aromatic ring can act as an hydrogen bond acceptor (via the $π$ electron density) and/or a hydrogen bond donor (via the CH groups), with the potential for cooperative effects. Our analysis places benzene at the centre of our frame-of-reference, and reveals for the first time that in solution the O-H$\cdotsπ$ interaction is highly localised and directional, the hydrogen atom being located directly above/below the ring centroid at a distance of 2.30 Å and with the hydroxyl bond axis normal to the aromatic plane. The tendency of methanol to form chain and cyclic motifs in the bulk liquid is manifest in a highly templated, symmetrical equatorial solvation structure; the methanol molecules surround the benzene so that the O-H bonds are coplanar with the aromatic ring while the oxygens interact with C-H groups through simultaneous bifurcated hydrogen bonds. By contrast, C-H$\cdotsπ$ interactions are relegated to the role of more distant spectators. The experimentally observed solvation therefore demonstrates that weak hydrogen bonding can give rise to strongly-ordered cooperative structural motifs also in the liquid phase.

cond-mat.soft↗

arXiv2022

Weak Interactions in Dimethyl Sulfoxide (DMSO) -- Tertiary Amide Solutions: the Versatility of DMSO as a Solvent

The structures of equimolar mixtures of the commonly used polar aprotic solvents dimethylformamide (DMF) and dimethylacetamide (DMAc) in dimethylsulfoxide (DMSO) have been investigated via neutron diffraction augmented by extensive hydrogen/deuterium isotopic substitution. Detailed 3-dimensional structural models of these solutions have been derived from the neutron data via Empirical Potential Structure Refinement (EPSR).The intermolecular Centre-of-Mass (CoM) distributions show that the first coordination shell of the amides comprises 13-14 neighbours, of which approximately half are DMSO. In spite of this near ideal coordination shell mixing, the changes to the amide-amide structure are found to be relatively subtle when compared to the pure liquids. Analysis of specific intermolecular atom-atom correlations allows quantitative interpretation of the competition between weak interactions in solution. We find a hierarchy of formic and methyl C-H to O hydrogen bonds form the dominant local motifs, with peak positions in the range 2.5-3.0 Å. We also observe a rich variety of steric and dispersion interactions, including those involving the amide pi-backbones. This detailed insight into the structural landscape of these important liquids demonstrates the versatility of DMSO as a solvent and the unparalleled resolution of neutron diffraction, which is critical for understanding weak intermolecular interactions at the nanoscale and thereby tailoring solvent properties to specific applications.

cond-mat.soft↗