[gmx-users] pressure for ambient water

Amit Choubey kgp.amit at gmail.com
Sun May 16 22:27:25 CEST 2010

Hi Everyone,

I was doing MD with SPC waters and found something which i am not sure how
to explain.

I made a box of SPC water of dimension 4x4x4 nm^3 and filled with water
using grenbox .

I then did a nvt simulation at 300 K for 1 ns . I used berendsen coupling
and Reaction - Field for coulomb interaction. Cut off were all set to 1
nm. Temperature did converge to 300 K. After this i turned of nvt and did
nve with RF-zero for another ns. Energy was well converged during this (RMSD
< 0.1 %). Temperature was also around 304 K (RMSD < 1%). But the pressure
was 1.1 Kilobar with a fluctuation of 20 % . I don understand this, shouldnt
this be around 1 bar ? Could some one suggest whats on ?

Thank you,
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