[gmx-users] NPT and NVT ensembles

Justin A. Lemkul jalemkul at vt.edu
Fri May 20 13:04:45 CEST 2011

ahmet yıldırım wrote:
> Dear Justin,
> In the first tutorial You said "After we arrive at the correct 
> temperature (based on kinetic energies), we will apply pressure to the 
> system until it reaches the proper density." That is, you apply each NVT 
> and NPT ensembles when you did the position restraints. Would not it 
> only be sufficient to implement NPT ensemble on the system? Is it 
> compulsory to apply both the x and y?
> For example:
> I get proper density and stabilized the temperature of the system though 
> I implement NPT ensemble on the system (not your tutorial sample).

Do whatever suits your system.  The tutorial is just one example, albeit a 
common one.  Some systems are robust enough to undergo NPT only, but I have seen 
cases where the application of pressure coupling to an unequilibrated system has 
led to the immediate collapse of the system, whereas NVT + NPT was stable.



Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080


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