Modern chemical engineering is increasingly turning to electrification—using microwave, electric, or magnetic fields—to intensify reactions and separations. However, when microwaves interact with solid surfaces and fluid molecules, they create complex interfacial polarization and induce fluid structures (specific arrangements of molecular clusters) that conventional thermodynamic models cannot accurately describe. In a perspective published in Frontiers of Chemical Science and Engineering, researchers at Nanjing Tech University introduce a new concept called equivalent potential (V_eq) to unify the effects of microwave fields and interfaces from a quantum‑mechanical foundation.
Traditional theories, such as statistical associating fluid theory, rely on macroscopic experimental data and cannot capture the microscopic structural changes caused by microwaves. The team instead starts from the Schrödinger equation and separates the Hamiltonian into intra‑cluster contributions and contributions from the surrounding microenvironment. The latter—including external field energy, interfacial geometric constraints, and electronic effects—is lumped into V_eq. This equivalent potential acts as an effective energy function that sums all environmental influences on fluid molecules.
Using implicit solvation models, the researchers computed Raman spectra of water molecules under different dielectric constants. A higher dielectric constant (stronger V_eq) shifts spectral peaks and narrows peak distribution, indicating constrained molecular motion and fewer accessible microstates. Real interfaces are asymmetric: some surface sites strongly interact with molecules (active sites), others weakly (inactive sites), and microwave can further intensify selected sites. This asymmetry leads to a broader distribution of molecular states.
Molecular dynamics simulations of water between graphite layers showed that applying an excess V_eq gradient forces water molecules from disordered four‑coordinated networks into highly ordered, isolated arrangements near the interface. However, raising the temperature (microwave thermal effect) can destroy this order, revealing a competition between V_eq‑induced ordering and thermal disorder.
The team further proposes using the Stark effect to calculate the minimum V_eq needed to transform one fluid structure into another. By constructing a Born‑Haber cycle between two cluster states, researchers can determine the required equivalent potential, enabling rational design of fluid structures for targeted properties.
Looking forward, validating V_eq in real systems requires advanced in‑situ characterizations with high spatiotemporal resolution, such as time‑resolved photoemission electron microscopy or tip‑enhanced Raman scattering. Combining artificial intelligence with this equivalent potential framework could enable high‑throughput screening of materials and microwave parameters, accelerating the development of energy‑efficient, electrified chemical processes.
This work provides a fundamental principle to model and regulate fluid structures under external fields, paving the way for rational design in microwave‑assisted chemical engineering.
ENGINEERING Chemical Engineering
Experimental study
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Equivalent potential: the nexus of microwave and interface for modeling and regulating fluid structures
15-Mar-2026