How to fix Erros:"Domain too large" and "segmentation Fault"

As suggested by steve in one of the posts I tried outputing values at every time step and the atoms are getting lost(ERROR: Lost atoms: original 209500 current 209499).

Kindly find the input file below. Would request help in figuring what the problem is as when I reduce the size of simulation box in z these errors do not occur.

Thank you.

BR/Joseph

# LJ potentials

pair_style lj/cut 2.2
pair_coeff * * 1.0 1.0
pair_coeff 1 2*3 0.6 1.0
pair_modify shift yes

# define groups

group lower region btm_wall
group upper region top_wall
group boundary union lower upper
group flow subtract all boundary

set group flow type 1
set group lower type 2
set group upper type 3

# initial velocities

compute mobile flow temp
velocity flow create 1.10 482748 temp mobile units box
thermo_modify temp mobile

# thermostating

compute mobile_thermo all temp/partial 0 0 1
fix 2 all langevin 1.10 1.10 1.0 699483
fix 1 all nve
fix_modify 2 temp mobile_thermo
thermo_modify temp mobile_thermo

# Couette flow

velocity lower set 0.0 0.0 0.0 units box
velocity upper set 1.0 0.0 0.0 units box
fix 3 boundary setforce 0.0 0.0 0.0

variable pxy equal pxy

#fix 5 flow ave/spatial 1 500 500 x center 12.136 z center 7.22 y 1.5 1.02375 vx region fluid file vel_fb.profile units box
#fix 6 flow ave/spatial 1 700000 700000 x center 12.136 z center 7.22 y 1.0 1.02375 density/mass region fluid file den_1.profile units box
#fix 7 flow ave/spatial 1 700000 700000 x center 12.136 z center 7.22 y 0.5 1.02375 density/mass region fluid file den_2.profile units box
#fix 8 all ave/time 1 700000 700000 v_pxy file pres_fb.dat

# Run

timestep 0.005
thermo 1

dump 1 all atom 1 dump.flow

run 400000

As suggested by steve in one of the posts I tried outputing values at
every time step and the atoms are getting lost(ERROR: Lost atoms:
original 209500 current 209499).

the domain too large error has to be a secondary error caused
some other problem due to unstable dynamics.

Kindly find the input file below. Would request help in figuring what
the problem is as when I reduce the size of simulation box in z these
errors do not occur.

without a complete input, it is difficult to debug this.

first thing that i would try in your place, is to lower the timestep.

axel.

Thanxx.. Lowering the timestep has fixed the problem.

BR/Joseph