Helium Compression Chamber: an ab initio molecular dynamics approach to chemical reactions under pressure
7 affiliations
- 1Donostia International Physics Center, Paseo Manuel de Lardizabal 4, Donostia-San Sebastian, Spain, 20018
- 2Dipartimento di Scienze Chimiche, della Vita e della Sostenibilitá Ambientale, Università degli Studi di Parma, Parco Area delle Scienze 11/a, Parma, Italy, 43124
- 3Department of Materials Science and Engineering
- 4Cornell University
- 5IKERBASQUE, Basque Foundation for Science, Plaza Euskadi 5,, Bilbao, Spain, 48009
- 6Departamento de Química Orgánica I, Facultad de Química/Kimika Fakultatea
- 7Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU)
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.
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BibTeX
@misc{laranjeira2026helium,
title = {{Helium Compression Chamber: an ab initio molecular dynamics approach to chemical reactions under pressure}},
author = {Jorge Laranjeira and Roberto Cammi and Maximilian Amsler and Bo Chen},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15009768/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009768/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Helium Compression Chamber: an ab initio molecular dynamics approach to chemical reactions under pressure
AU - Jorge Laranjeira
AU - Roberto Cammi
AU - Maximilian Amsler
AU - Bo Chen
PY - 2026
DA - 2026/10/02
PB - ChemRxiv
DO - 10.26434/chemrxiv.15009768/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009768/v1
AB - 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.
ER -