[gmx-users] Fattal error in npt_umbrella : Umbrella Sampling Simulations tutorial

[Alexander Alexander]

Dear Gromacs user,

I am trying to do the Umbrella simulation following exactly the the
tutorial, everything is fine but I a fatal error happens in .tpr file
generation of npt_umbrella section warning about Pcoupl in npt_umbrella.mdp
file.
I used the suggested .mdp file in tutorial with Parrinello-Rahman pressure
coupling, but it complained that this type of coupling make the
equilibration unstable, and use Berendsen pressure coupling instead.
Then, I did, but again Fatal error by an warning stating that Berendsen
invalidates the true ensemble for the thermostat.

All the inputs and even the name are fully identical with the tutorial
samples.
The version of Gromacs is : VERSION 5.1-rc1

Any suggestion would be highly appreciated.

Best regards,
Alex