Hydrogen-Bond Network in Equimolar N-Methylacetamide-Water: Integrated Neutron Scattering, Molecular Dynamics,...

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Materials Science

Background:

• Understanding liquid mixtures is crucial for chemical processes.
• N-methylacetamide-water (NMA-W) mixtures are relevant in various chemical applications.
• Previous studies have provided neutron scattering data for NMA-W.

Purpose of the Study:

• To re-examine NMA-W mixtures using advanced computational techniques.
• To analyze the electronic structure of hydrogen bonds in NMA-W.
• To correlate electronic interactions with hydrogen bond lifetimes and network topology.

Main Methods:

• Molecular dynamics (MD) simulations with AMBER force field and SPC/E water model.
• Density Functional Theory (DFT)-based Natural Bond Orbital (NBO) and Atoms-in-Molecules (AIM) analyses.
• Data-driven reconstruction using Random Forest Regressor for scattering functions.

Main Results:

• MD simulations accurately reproduced experimental structure factors and pair correlation functions.
• Random Forest Regressor provided a continuous numerical representation of scattering data.
• NBO and AIM analyses revealed details of hydrogen bond electronic structure, including charge transfer.
• Stronger electronic interactions did not consistently correlate with longer hydrogen bond lifetimes.

Conclusions:

• Liquid structure is governed by local NMA-water cluster arrangements.
• Intermolecular interactions are characterized by specific electronic and topological features.
• Hydrogen bond dynamics depend on both electronic strength and local network topology, not solely on interaction strength.