[gmx-users] Simulations in NVE ensemble with CHARMM36

[ABEL Stephane 175950]

Dear GMX-users

I have done a 90 ns long simulation of a heterogeneous  system (SPCE water, phospholipids and a hydrophobic solvent) in NPT ensemble (298 K at 1 bar) with GROMACS4.6.5. to compute related dynamical properties, I would like to continue this simulation in NVE. But I am puzzled to choose the mdp parameters to have a good energy conservation. Indeed, I have checked the gromacs 2004 JCTC or the following and follow the advices given in the following threads

http://comments.gmane.org/gmane.science.biology.gromacs.user/42686
https://www.mail-archive.com/gmx-users@gromacs.org/msg60393.html

But I always obtain for my system a large drift and the temp decreases significantly (20 K) after few dozens of ps (the initial temp was around 297.3 K). For this simulation I used the double precision of gromacs with a timestep of 1 fs. 

More, since I have never used the potential-modifier features, so I not sure how to setup  the correct parameters in the context of CHARMM simulations. 

Could you help and provides some advices

Thanks

Stephane