[lammps-users] temper/grem and NPT simulations


I want to use the generalized replica exchange method on my system and I use the “temper/grem” command for this purpose!
The swap between adjacent ensembles when I use NPT simulation does not happen but when I change the NPT simulation to the NVT simulation this swap occurs!

Can you please let me know what can be the problem in this case?



Can somebody tell me why the “fix temper/grem” command doesn’t work with NPT simulations?

I suggest you contact the author who is listed at the top of the src/REPLICA/temper_grem.cpp file.
Probably this implementation was not designed to work with NPT, only NVT. And it
needs to be extended.

There is also a temper/npt command if you want to try it.


Dear Steve,

Thanks for your reply.
The temper/grem command works with
the NPT simulations when the pair_style is “lj/cut”
but when I use TIP4P water model pair_style, it does not show any swap between replicas!

On the other hand in LAMMPS documentation no restriction is mentioned about this fix command!


What fix command?

If you mean a note in the doc page for temper/grem, then I don’t think it’s an issue with the command.

If a tempering method makes no swaps it is typically b/c there is not sufficient
overlap in the adjacent temperature states to “accept” the swap. That may be a function
of the model. But that is up to you as the user of a tempering command to figure out.
It’s typically not something the tempering method is smart enough to figure out. As least
not for the implementations in LAMMPS.