Molecular Interactions and Solvation Dynamics in Aqueous Systems

Aqueous systems are governed by a delicate balance of intermolecular forces that dictate structure, dynamics and reactivity at interfaces and in bulk solution. Central to these phenomena are hydrogen bonds, ion–water interactions and dispersion forces, which collectively shape solvation shells around dissolved species. The formation and rearrangement of these solvation layers occur over a wide range of timescales, from femtoseconds for vibrational relaxation to nanoseconds for diffusion and exchange processes. Advances in ultrafast spectroscopy, neutron and X-ray scattering, and state-of-the-art simulations have revealed the importance of cooperative networks and nuclear quantum effects in modulating solvation dynamics, with profound implications for fields as diverse as catalysis, energy storage, environmental chemistry and biophysics.

Recent efforts have emphasised the integration of experimental and theoretical approaches. Machine-learning potentials trained on ab initio path-integral molecular dynamics allow access to long timescales without sacrificing quantum mechanical accuracy. Concurrently, quantum cluster equilibrium models have provided an atomistic framework for predicting thermodynamic properties such as the ionic product of water by sampling low-populated ionic species. Together, these tools are reshaping our understanding of how molecular interactions evolve and how they influence macroscopic properties of aqueous media.

Research from Nature Portfolio

Recent studies have demonstrated that neural-network potentials trained on ab initio path-integral molecular dynamics can accurately capture the vibrational spectrum and phase-transition behaviour of molecular systems. In the case of ammonia, high-resolution inelastic neutron scattering combined with machine-learning-based simulations revealed that nuclear quantum effects critically influence both low-energy intermolecular modes and high-frequency N–H stretches, providing a transferable framework to study quantum effects in other hydrogen-bonded liquids.

Separately, first-principles quantum cluster equilibrium calculations have been employed to predict the ionic product of water across a range of temperatures. By evaluating Boltzmann-weighted ensembles of ion-pair clusters, researchers recovered semi-quantitative agreement with experimental data and identified dominant cluster motifs that hinder recombination of hydronium and hydroxide ions, elucidating the mechanistic underpinnings of water autoionisation from a quantum-chemical perspective.

Molecular Interactions and Solvation Dynamics in Aqueous Systems publication trend

The graph below shows the total number of articles in molecular interactions and solvation dynamics in aqueous systems across all publications each year (not limited to Nature Index journals).

Technical terms

Hydrogen bond: A directional non-covalent interaction between a hydrogen atom covalently bound to an electronegative atom and a lone pair on another electronegative atom, crucial for structuring liquid networks.

Solvation shell: The organised layer(s) of solvent molecules directly surrounding a solute, stabilising it through electrostatic and hydrogen-bond interactions.

Nuclear quantum effects (NQEs): Quantum mechanical phenomena such as zero-point motion and tunnelling that influence the positions and vibrations of light nuclei, notably in hydrogen-bonded systems.

Path-integral molecular dynamics (PIMD): A simulation technique that incorporates NQEs by representing each quantum nucleus as a ring polymer of fictitious particles connected by harmonic springs.

Quantum cluster equilibrium (QCE): A statistical-thermodynamic method that models liquids as an ensemble of clusters of varying sizes and compositions, weighted by quantum-chemical energies.

Extended X-ray absorption fine structure (EXAFS): A spectroscopic technique that probes local atomic structure by analysing oscillations in X-ray absorption above an element’s absorption edge.

References

1. Neutron scattering and neural-network quantum molecular dynamics investigation of the vibrations of ammonia along the solid-to-liquid transition. Nature Communications (2024).
2. EXAFS Study on the Coordination Chemistry of the Solvated Copper(II) Ion in a Series of Oxygen Donor Solvents. Inorganic Chemistry (2020).
3. Hydrated Sodium Ion Clusters [Na+(H2O)n (n = 1–6)]: An ab initio Study on Structures and Non-covalent Interaction. Frontiers in Chemistry (2019).
4. Hydrogen Bonding in Liquid Ammonia. The Journal of Physical Chemistry Letters (2022).
5. The Ionic Product of Water in the Eye of the Quantum Cluster Equilibrium. Molecules (2022).