[gmx-users] Pressure Coupling in GROMACS

[Jashimuddin Ashraf]

Dear GROMACS users,

I am new to GROMACS. My system contains only carbon nanotubes and inside my
md.mdp file I have-

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.
.
Pcoupl                   = berendsen
Pcoupltype               = isotropic
tau_p                    = 1            ; @pressure coupling 1ps
compressibility          = 4.5e-5        ;
ref_p                    = 1.0            ; @reference pressure
.
.
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whenever I run the grompp command, I get a warning called-


----------------------------------------------------------------------------------------------------------------------------

Using Berendsen pressure coupling invalidates the true ensemble for the
thermostat
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I looked up at the mail list where I found Parrinello-Rahman to be
appropriate for the NPT simulations. But I intend to run production MD. Is
this an error to be
worried about? (I can obviously run simulations using maxwarn)

I have another problem. When I simulated carbon nanotubes with water/ other
molecules, the average pressure I observed from simulation (using g_energy
command) had a good agreement with the ref_p. But now the average pressure
becomes independent of my ref_p. This is a problem that is bugging me for a
long time. How can I resolve this?

Thanks in advance.