I read some articles about the molecular dynamics simulation, in which some simulations adopting the reactive force-field while other simulations using the non-reactive force-field, so what's the difference between them and in what conditions can these force field can be adopted?
Force fields are classical descriptions of usually pair interactions between atoms, including bonds. In non-reactive force field description, bonds can be stretched and twisted in interactions with the other atoms or molecules in the neighbourhood, but cannot be broken. Thus, chemical reactions cannot be simulated. Reactive force fields have additional terms (related to bond order concept) that modify the bond strength (i.e. pair potential) depending on the environment. This allows molecular bonds to be broken an re-formed and chemical reactions to take place in a simulation without using quantum mechanics.
One example: "We have adopted this force field because it was found to have less than 10% deviation from experimental results as far as interfacial properties are concerned."
cited from 2017 Surface dissimilarity affects critical distance of influence for confined water
Molecular dynamics using the general bond-order-dependent ReaxFF reactive force field can be used to simulate bond breaking and both intra- and inter-molecular bond formation during the
rapid, high temperature heating of kerogen. The ReaxFF force field, which has been widely used to study the pyrolysis and combustion of hydrocarbon systems, enables the simulation of chemical reactions without the computational burden of quantum mechanical molecular dynamics, and systems with thousands of atoms as well as their chemical reactions can be investigated.
cited from 2017 Reactive Molecular Dynamics Simulation of Kerogen Thermal Maturation and Cross-Linking Pathways
Force fields are classical descriptions of usually pair interactions between atoms, including bonds. In non-reactive force field description, bonds can be stretched and twisted in interactions with the other atoms or molecules in the neighbourhood, but cannot be broken. Thus, chemical reactions cannot be simulated. Reactive force fields have additional terms (related to bond order concept) that modify the bond strength (i.e. pair potential) depending on the environment. This allows molecular bonds to be broken an re-formed and chemical reactions to take place in a simulation without using quantum mechanics.
Thanks, Janka
So the take home message is non-reactive force field is useful for physical process (no chemical reaction, therefore, no new materials generated), while the reactive force field is adopted for chemical reaction because there exists new bonds generated.
Exactly. Non-reactive force fields can simulate mixing, flows, electrochemical processes, behaviour at interfaces, some phase transitions, transport properties... They can do a lot, but no chemical reactions. If you use reactive force fields to represent molecules and make a mixture in a simulation, you can have reactions in addition to flows.
The reactive force field (ReaxFF), which was developed by van Duin et al., is an empirical force field for molecular dynamics (MD). It is capable of describing bond-cleavage and cross-linking reactions with a low computational cost and accuracy close to the quantum chemical method. ReaxFF MD has been applied to explore the mechanisms of molecular systems with thousands of atoms. In particular, this method has been widely used to explore reactions of coal macromolecules in various environments.
cited from Pyrolysis Mechanism of Metal-Ion-Exchanged Lignite: A Combined Reactive Force Field and Density Functional Theory Study
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