[DFTB-Plus-User] How fast is DFTB+ in MD simulation?

[Moyassar Meshhal]

Hello DFTB+ community,

I've noticed that DFTB+ is super fast as well as efficient in geometry optimization.
On contrary, in MD it's relatively slow compared to DFTB in CP2K.

For a system consists of about 250 atoms (C, H and O) in a box of water (250-300 water molecules), DFTB+ produces about 800 steps per day using 16 cpus, and increasing the number of cpus up to 32 does not show much improvement in fastening the simulation. On the other hand, CP2K is about 8-10 times faster. But DFTB+'s results are much reliable than cp2k.

Does this sound normal? As if it is normal, one would expect that it may take about 2 months to get a long MD trajectory for each of my systems!
Is there any way to make the calculations faster?

On the "dftbplus-recipes" website, SCC-MD could be speeded up by using the extended Lagrangian (XL) scheme, however, according to the manual: "The extended Lagrangian implementation only works for the (N,V,E) ensemble so far, so neither thermostats nor barostats are allowed."
So, it does not apply in my case as I do NVT MD.

Best Regards,
Moyassar


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