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As far as I know, we need force fields such as Tersoff/Coulomb potentials when performing MD simulations. In AIMD, we use pseudopotentials similar to DFT.

Which method should we classify AIMD to: a group of MD methods or a group of DFT methods?

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2 Answers 2

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Purely classical MD would use a classical forcefield to do MD,
whereas ab initio MD (AIMD) would usually involve DFT calculations to obtain the forces, then the same type of MD procedure can be used for the dynamics.

Technically the forces could also be calculated with MP2 or coupled cluster methods, or any other ab initio method, so it does not need to involve DFT to be "ab initio MD", but in practice people don't usually use these "other" ab initio methods for the forcefields, and that is for good reasons (e.g. it could make the calculations too slow).

As for your question of whether AIMD is classified as an MD method or a DFT method, I'd say it's an MD method that usually uses DFT (but does not have to use DFT). More simply: it's a flavor of MD. It's not a DFT method, or a flavour of MD, it just usually uses DFT as one part of the procedure.

You might also be interested in this thread: What are the types of ab initio Molecular Dynamics?

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Ab initio molecular dynamics (AIMD) involves both ab initio and molecular dynamics (MD). If the ab initio is done by density functional theory (DFT), the method is both a density functional and MD method, and the question is based on a false dichotomy.

Nike's answer correctly points out that the ab initio calculations can also be run with another method. I would like to add that the sentence in the question

In AIMD, we use pseudopotentials similar to DFT.

is not necessarily true; AIMD calculations are often run with DFT also without pseudopotentials.

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