Reactive Molecular Dynamics Simulations of Mechanochemical Ammonia Production
4 affiliations
- 1Mechanical and Industrial Engineering, Universitas Gadjah Mada, Jl. Grafika No. 2, Yogyakarta, Indonesia, 55281
- 2Mechanical Engineering
- 3Imperial College London
- 4University of Bath
Abstract
Green ammonia production will be crucial to achieving global net-zero emissions. The current dominant technology for producing ammonia, known as the Haber-Bosch process, requires extreme temperatures and pressures. One promising alternative is mechanocatalysis, where mechanical energy is used to promote reactivity and reduce energy consumption. Ammonia production via mechanocatalysis has recently been demonstrated at the laboratory scale. A deeper understanding of the kinetics and mechanism of this reaction is necessary to facilitate scale-up of this process. However, this is challenging to obtain inside ball mills, the most commonly used devices for mechanocatalysis. Here, we use molecular dynamics simulations to study mechanocatalytic ammonia production. A reactive force field is employed to investigate the effect of applied stress on nitrogen dissociation and hydrogenation on an iron catalyst. We find that the activation energy of the nitrogen dissociation step decreases from 56 kJ/mol in the thermally activated process on Fe(111), to 29 kJ/mol under a normal stress of 5 GPa. For the less reactive Fe(110) surface, the reduction is even more significant, from 117 kJ/mol to 35 kJ/mol. The larger activation volume for Fe(110) than Fe(111) is due to deeper penetration of the nitrogen molecules into the more open surface. The hydrogenation step was also accelerated under applied stress, although the effect was less pronounced than for nitrogen dissociation. These trends are quantified using SATA equation framework, providing the first SATA analysis of mechanochemical ammonia synthesis. We also reveal the atomic-scale mechanism of this stress-enhanced reactivity, which does not require increased defect density in the iron catalyst. The mechanistic analysis reveals that normal stress promotes Fe–N bond formation, which weakens the N–N bond and lowers the activation barrier. This is distinct from non-catalytic mechanochemistry, where normal stress typically inhibits bond-breaking reactions. Nitrogen dissociation can be further accelerated by the application of shear stress, which can promote the reaction at room temperature. These results provide an improved fundamental understanding that could help to guide further improvements in the efficiency of mechanochemical ammonia production.
Related
- Interpretable Machine Learning of Hydrogen Production from Reactive Molecular Dynamics Simulations of Polyethylene Oxidative Gasification
- Reactive molecular dynamics simulations of atenolol first steps degradation by 9CL6 ammonia monooxygenase
- SO3LR Tauri: Generally Applicable Force Fields for Reactive (Bio)Molecular Simulations Covering the Periodic Table
- Interfacial Mechanisms of Reactive Dye Adsorption on a Waste-Cotton Derived PVA/TiO2/Cellulose Biofilm: A Molecular Dynamics and Physics-Informed Predictive Framework
- NEVPT2 Multiple Spawning Molecular Dynamics Simulations for Uracil
BibTeX
@misc{rahman2026reactive,
title = {{Reactive Molecular Dynamics Simulations of Mechanochemical Ammonia Production}},
author = {Muhammad Aulia Rahman and Daniele Dini and James P. Ewen},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008447/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008447/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Reactive Molecular Dynamics Simulations of Mechanochemical Ammonia Production
AU - Muhammad Aulia Rahman
AU - Daniele Dini
AU - James P. Ewen
PY - 2026
DA - 2026/09/07
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008447/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008447/v1
AB - Green ammonia production will be crucial to achieving global net-zero emissions. The current dominant technology for producing ammonia, known as the Haber-Bosch process, requires extreme temperatures and pressures. One promising alternative is mechanocatalysis, where mechanical energy is used to promote reactivity and reduce energy consumption. Ammonia production via mechanocatalysis has recently been demonstrated at the laboratory scale. A deeper understanding of the kinetics and mechanism of this reaction is necessary to facilitate scale-up of this process. However, this is challenging to obtain inside ball mills, the most commonly used devices for mechanocatalysis. Here, we use molecular dynamics simulations to study mechanocatalytic ammonia production. A reactive force field is employed to investigate the effect of applied stress on nitrogen dissociation and hydrogenation on an iron catalyst. We find that the activation energy of the nitrogen dissociation step decreases from 56 kJ/mol in the thermally activated process on Fe(111), to 29 kJ/mol under a normal stress of 5 GPa. For the less reactive Fe(110) surface, the reduction is even more significant, from 117 kJ/mol to 35 kJ/mol. The larger activation volume for Fe(110) than Fe(111) is due to deeper penetration of the nitrogen molecules into the more open surface. The hydrogenation step was also accelerated under applied stress, although the effect was less pronounced than for nitrogen dissociation. These trends are quantified using SATA equation framework, providing the first SATA analysis of mechanochemical ammonia synthesis. We also reveal the atomic-scale mechanism of this stress-enhanced reactivity, which does not require increased defect density in the iron catalyst. The mechanistic analysis reveals that normal stress promotes Fe–N bond formation, which weakens the N–N bond and lowers the activation barrier. This is distinct from non-catalytic mechanochemistry, where normal stress typically inhibits bond-breaking reactions. Nitrogen dissociation can be further accelerated by the application of shear stress, which can promote the reaction at room temperature. These results provide an improved fundamental understanding that could help to guide further improvements in the efficiency of mechanochemical ammonia production.
ER -