[gmx-users] Question about nsttcouple

minky son minky0710 at gmail.com
Wed Nov 7 15:43:37 CET 2018

Dear gmx users,

In gromacs manual,

“nsttcouple: The default value of -1 sets nsttcouple equal to nstlist,
unless nstlist <=0, then a value of 10 is used.”

When I did grompp with the following mdp options,

nstlist = 20

tcoupl = berendsen

nsttcouple = -1

tau-t = 0.1

I got a warning message.

WARNING 1 [file pr_nvt.mdp]:

  "For proper integration of the Berendsen thermostat, tau-t (0.1) should
be at least 5 times larger than nsttcouple*dt (0.04)"

I think this means that nsttcouple is applied to 20, not 10. This doesn't
match with the one mentioned in the manual. why?

When I also tried nstlist=10, grompp didn’t show any warning.

But the value of nstlist was automatically changed to 40 in mdrun.

Is nsttcouple applied to 10 in this case?

Please give me an advice.

Thank you.

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