[gmx-users] Osmotic pressure

[gozde ergin]

Hey Justin, 

These result was with Parinello-Rahman.
Here is the  setting for T and P coupling;

; Temperature coupling
tcoupl                   = berendsen
tc-grps                  = System
tau_t                    = 1.0
ref_t                    = 300
; Pressure coupling is on
pcoupl              = Parrinello-Rahman   
pcoupltype          = semiisotropic     
tau_p               = 2.0 2.0         
ref_p               = 150.0 1.0         
compressibility     = 0 4.5e-5        
refcoord_scaling    = com
; Periodic boundary conditions
pbc     = xyz                   ; 3-D PBC
; Dispersion correction
DispCorr    = no   

> On 18 Apr 2016, at 15:48, Justin Lemkul <jalemkul at vt.edu> wrote:
> 
> 
> 
> On 4/18/16 4:43 AM, gozde ergin wrote:
>> In Roux study they did 10 independent 1.5 ns production simulation and I did 15 ns simulation and divided it to 10 1.5ns simulations.
>> 
>> Osmotic pressure for 5M : My result 216.8 (+/- 0.2 bar)
>>                                           Roux study 300    (+/- 10  bar)
>>                                           Experiment 300 bar
> 
> Your fluctuation seems unreasonably low.  Is this still with Berendsen?  If so, repeat it using Parrinello-Rahman for the barostat.  This result should be quite reproducible when using the method described exactly in the paper.
> 
> -Justin