Npt equilibration

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Hello,
While I am running an npt equilibration, the following message appears and the run stopped.
“Step 800 Warning: pressure scaling more than 1%, mu: 0.9334 0.9334 0.9334
Segmentation fault (core dumped)”

the npt.mdp file settings:

title = NPT equilibration
define = -DPOSRES ; position restrain the protein
; Run parameters
integrator = md ; leap-frog integrator
nsteps = 2500000 ; 2 * 2500000 = 5000 ps
dt = 0.002 ; 2 fs
; Output control
nstxout = 500 ; save coordinates every 1.0 ps
nstvout = 500 ; save velocities every 1.0 ps
nstenergy = 500 ; save energies every 1.0 ps
nstlog = 500 ; update log file every 1.0 ps
; Bond parameters
continuation = yes ; Restarting after NVT
constraint_algorithm = lincs ; holonomic constraints
constraints = h-bonds ; bonds involving H are constrained
lincs_iter = 1 ; accuracy of LINCS
lincs_order = 4 ; also related to accuracy
; Nonbonded settings
cutoff-scheme = Verlet ; Buffered neighbor searching
vdwtype = cutoff
vdw-modifier = force-switch
ns_type = grid ; search neighboring grid cells
nstlist = 10 ; 20 fs, largely irrelevant with Verlet scheme
rvdw-switch = 1.0 ; short-range van der Waals cutoff (in nm)
rvdw = 1.2
rlist = 1.4
dispcorr = no
; Electrostatics
coulombtype = PME ; Particle Mesh Ewald for long-range electrostatics
rcoulomb = 1.2 ; short-range electrostatic cutoff (in nm)
pme_order = 4 ; cubic interpolation
fourierspacing = 0.16 ; grid spacing for FFT
; Temperature coupling is on
tcoupl = V-rescale ; modified Berendsen thermostat
tc-grps = System
tau_t = 1.0
ref_t = 300
; Pressure coupling is on
pcoupl = C-rescale
pcoupltype = isotropic ; uniform scaling of box vectors
tau_p = 5.0 ; time constant, in ps
ref_p = 1.0 ; reference pressure, in bar
compressibility = 4.5e-5 ; isothermal compressibility of water, bar^-1
refcoord_scaling = com
; Periodic boundary conditions
pbc = xyz ; 3-D PBC
; Velocity generation
gen_vel = no ; Velocity generation is off

How to resolve the issue. Thank you

Your settings look OK, so it’s probably a system instability issue. Try if it helps extending the NVT equilibration before switching to NPT.

If that does not help, it might be that your simulation box deforms quickly when applying pressure coupling. In that case, see if it helps increasing tau_p, try tau_p=25. If that helps, you might want to run another follow-up NPT equilibration with tau_p=5.