GROMACS version: 2020.2
GROMACS modification: Yes
I used CHARMM36 for a MD job of a homodimer protein (no cofactors). Everything looks fine in terms of the preparation (em, neutralization, nvt and npt equlibrations), but after 50 ns of the md simulation the dimers repeatedly separate and then come back. This is after corrections with trjconv (gmx trjconv -s md.tpr -f md.xtc -o md_processed.xtc -center -pbc mol -ur compact). Is this something to do with trjconv no processing properly or my system is really unstable with this force field? The same system is well behaved even at 200 ns with OPLS-AA/L. Any suggestions on what’s happening here?
my md parameters:
integrator = md
nsteps = 100000000
dt = 0.002
nstenergy = 5000
nstlog = 5000
nstxout-compressed = 5000
continuation = yes
constraint_algorithm = lincs
constraints = h-bonds
lincs_iter = 1
lincs_order = 4
cutoff-scheme = Verlet
nstlist = 40
vdwtype = cutoff
vdw-modifier = potential-shift-Verlet
coulombtype = PME
tcoupl = V-rescale
tc-grps = Protein Non-Protein
tau_t = 0.1 0.1
ref_t = 300 300
pcoupl = Parrinello-Rahman
pcoupltype = isotropic
tau_p = 2.0
ref_p = 1.0
compressibility = 4.5e-5
pbc = xyz
DispCorr = no
gen_vel = no