[gmx-users] Regarding error in NPT SIMULATION in VACUM

[vidhya sankar]

Dear Justin Thank you for your previous reply
                                                                     When I run NPT equlibiriation for My CNT CNCASSED CYCLICPETIDE in VACUM
I have Got the Following error after 3 lacs steps out of 10 lacs

The X-size of the box (7.750338) times the triclinic skew factor (1.000000) is smaller than the number of DD cells (8) times the smallest allowed cell size (0.969134)

My Box size is 10.83680  10.88700  10.19300
MY NPT parameters are
title        = NPT Equilibration for KALP15-DPPC
define        = -DPOSRES   ; position restrain the protein
; Run parameters
integrator    = md        ; leap-frog integrator
nsteps        = 1000000    ; 2 * 500000 = 1000 ps (1 ns)
dt         = 0.002        ; 2 fs
; Output control
nstxout        = 100        ; save coordinates every 0.2 ps
nstvout        = 100        ; save velocities every 0.2 ps
nstenergy    = 100        ; save energies every 0.2 ps
nstlog        = 100        ; update log file every 0.2 ps
; Bond parameters
continuation    = yes            ; Restarting after NVT
constraint_algorithm = lincs    ; holonomic constraints
constraints    = all-bonds            ; all bonds (even heavy atom-H bonds) constrained
lincs_iter    = 1                    ; accuracy of LINCS
lincs_order    = 4                    ; also related to accuracy
; Neighborsearching
ns_type        = grid        ; search neighboring grid cels
nstlist        = 5            ; 10 fs
rlist        = 0.9        ; short-range neighborlist cutoff (in nm)
rcoulomb    = 0.9        ; short-range electrostatic cutoff (in nm)
rvdw        = 1.4        ; short-range van der Waals cutoff (in nm)
; Electrostatics
coulombtype    = PME        ; Particle Mesh Ewald for long-range electrostatics
pme_order    = 4            ; cubic interpolation
fourierspacing    = 0.16        ; grid spacing for FFT
; Temperature coupling is on
tcoupl        = Nose-Hoover            ; More accurate thermostat
tc-grps        = Protein CNT    CL    ; three coupling groups - more accurate
tau_t        = 0.5      0.5    0.5            ; time constant, in ps
ref_t        = 323       323    323            ; reference temperature, one for each group, in K
; Pressure coupling is on
pcoupl        = Parrinello-Rahman        ; Pressure coupling on in NPT
pcoupltype    = isotropic            ; uniform scaling of x-y box vectors, independent z
tau_p        = 5.0                    ; time constant, in ps
ref_p        = 1.0    1.0                ; reference pressure, x-y, z (in bar)
compressibility = 4.5e-5    4.5e-5    ; isothermal compressibility, bar^-1
; Periodic boundary conditions
pbc            = xyz        ; 3-D PBC
; Dispersion correction
DispCorr    = EnerPres    ; account for cut-off vdW scheme
; Velocity generation
gen_vel        = no        ; Velocity generation is off
; COM motion removal
; These options remove motion of the protein/bilayer relative to the solvent/ions
nstcomm         = 1
comm-mode       = Linear
comm-grps       = CNT_protein  CL
; Scale COM of reference coordinates
refcoord_scaling = com

How to Solve this error?
 Please Help me Which Parameter Shoul I Cahnge in . mdp file?

Thanks in Advance