Helium Compression Chamber: an ab initio molecular dynamics approach to chemical reactions under pressure
Year: 2026
Type: preprint
Abstract: Understanding how pressure affects chemical reactivity requires methods capable of describing both the structural response of molecules and the thermodynamics of reactions under compression. We present the Helium Compression Chamber (HeCC), a computational approach in which molecules are compressed within an explicit helium environment and their reaction free energy profiles are determined from finite-temperature molecular dynamics simulations. An on-the-fly machine-learning force field is employed to make extensive sampling feasible while retaining ab initio accuracy for the underlying potential-energy evaluations. The pressure response of four representative reactions is investigated, including bond cleavage, electrocyclization, cycloaddition, and hydrogen transfer. The calculated free-energy profiles show that compression systematically favors reactions associated with a decrease in molecular volume, while the opposite trend is observed for cyclobutene ring opening. In particular, the Diels–Alder reaction becomes barrierless at sufficiently high pressure, whereas the barriers for hexatriene cyclization and the 1,5-hydrogen shift decrease progressively with compression. The structural changes along the reaction coordinates and the pressure dependence of the corresponding activation and reaction volumes are compared with predictions from the extreme pressure-polarizable continuum model (XP-PCM) method. The comparison illustrates both the consistency and the differences between explicit-and continuum-pressure descriptions. HeCC therefore offers a route toward finite-temperature simulations of chemical reactions under pressure and provides a foundation for extending such calculations to more realistic solvation environments.
Source: ChemRxiv
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7216274378