Particles outside surface of region

Hi all,

I am using lammps version 31 March, 2016. I want to simulate an isotropic liquid with gay berne interaction in a box (p p f) with periodic boundaries along x and y axes and non periodic boundary along z axis. I am using fix wall/region command. I am also changing the box’s z dimension. Also, I have used displace_atoms command to displace atoms so that they remain in box. But still I am getting the error ‘Particle outside surface of region used in fix wall/region’. Is still the problem in particle’s displacement or in the values of sigma and epsilon for wall-particle interaction or something else? My input script is provided below.

Thank you in advance.

units lj
atom_style ellipsoid
dimension 3

boundary p p p

lattice sc 0.05

region box block 0 15 0 15 0 24
create_box 1 box
create_atoms 1 box

set type 1 mass 1.0
set type 1 shape 3 1 1
set group all quat/random 18238

compute rot all temp/asphere

variable dof equal 2
compute_modify rot extra/dof ${dof}

velocity all create 2.4 87287 loop geom

pair_style gayberne 1.0 3.0 1.0 5.5
pair_coeff 1 1 3.0 1.0 1 1 1 1 1 1 5.0

neighbor 1.0 bin

variable step equal step
variable density equal density
variable temp equal temp
variable etotal equal etotal
variable pxx equal pxx
variable pyy equal pyy
variable pzz equal pzz
variable lx equal lx
variable ly equal ly
variable lz equal lz
variable zlo equal zlo
variable zhi equal zhi
variable xlo equal xlo
variable xhi equal xhi
variable ylo equal ylo
variable yhi equal yhi
variable pe equal pe

thermo_style custom temp press pe step xlo xhi lx ylo yhi ly zlo zhi lz

thermo 10

timestep 0.002

compute q all property/atom quatw quati quatj quatk

fix 1 all npt/asphere temp 1.0 1.0 0.1 iso 3.2 3.2 0.1 &
mtk no pchain 0 tchain 1
compute_modify 1_temp extra/dof ${dof}

fix 2 all print 10 “{step} {density} {temp} {etotal} {pxx} {pyy} {pzz} {lx} {ly} {lz} {xlo} {xhi} {ylo} {yhi} {zlo} {zhi}” file output1e.txt screen no title “step density temp etotal pxx pyy pzz lx ly lz xlo xhi ylo yhi zlo zhi”
run 20

unfix 2
unfix 1

fix 1 all nve

fix 2 all print 10 “{step} {density} {temp} {etotal} {pxx} {pyy} {pzz} {lx} {ly} {lz} {xlo} {xhi} {ylo} {yhi} {zlo} {zhi}” file output2e.txt screen no title “step density temp etotal pxx pyy pzz lx ly lz xlo xhi ylo yhi zlo zhi”

run 20

unfix 2

variable rljmin equal (2^(1.0/6.0))
variable delz atom -{zlo}+{rljmin}
variable z1hi equal ({zhi}-{zlo}+${rljmin})
variable z1lo equal 0.0
variable N equal count(all)
displace_atoms all move 0.0 0.0 v_delz units box

dump 1 all custom 10 dump.ellipse.gayberne id type x y z

thermo_style custom step temp press pe xlo xhi lx ylo yhi ly zlo zhi lz v_N

change_box all z final {z1lo} {z1hi} boundary p p f remap units box
region zlowall plane 0 0 0 0 0 1 units box
region zhiwall plane 0 0 {z1hi} 0 0 -1 units box fix lw all wall/region zlowall lj126 1.0 1.0 {rljmin}
fix_modify lw energy yes
fix rw all wall/region zhiwall lj126 1.0 1.0 ${rljmin}
fix_modify rw energy yes

fix 2 all print 10 "{step} {density} {temp} {pe} {etotal} {pxx} {pyy} {pzz} {lx} {ly} {lz} {xlo} {xhi} {ylo} {yhi} {zlo} ${zhi} " file output3e.txt screen no title “step density temp etotal pxx pyy pzz lx ly lz xlo xhi ylo yhi zlo zhi”
run 50

What the error message means is simple. One or more
of your particles has it’s position outside the region.
So the code cannot compute a wall/particle force. Since
your regions are simple planar surfaces, you should be
able to check yourself (viz, dump) when a particle moves
past the plane. Why that is happening is something
you need to figure out for your model and its dynamics.