trying to pull a CNT tube

Hello all,

I have a structure which is 6 CNT surrounding a center CNT.
I am trying to pull the center tube out of the structure with fix move command in dynamics.
The structure is not doing as expected. When i visualize the output only the top atoms
i am using to pull are being pulled out. The center tube as a whole should be pulled out.
I have checked everything in the input file and do not find anything wrong to my knowledge.
Any insight on what i am doing wrong? My input file is as below,

thanks,
Rohit.

Input file:

units metal
atom_style atomic
dimension 3
boundary f f f

read_data cntpull.data

1 to 7 are center tube followed by the surrounding 6 tubes, 8 to 14 are corresponding bottom most atoms of tube

mass 1 12
mass 2 12
mass 3 12
mass 4 12
mass 5 12
mass 6 12
mass 7 12
mass 8 12
mass 9 12
mass 10 12
mass 11 12
mass 12 12
mass 13 12
mass 14 12
mass 15 12 #top center atoms

group pull type 15 #type 15 is the centre top atoms to be pulled
group bottomm type 9 10 11 12 13 14

newton on
pair_style hybrid lj/cut 15 airebo 2 0 0
pair_coeff * * airebo …/potentials/CH.airebo C C C C C C C C C C C C C C C
pair_coeff 1 27 lj/cut 0.00238754 3.41571
pair_coeff 1 9
14 lj/cut 0.00238754 3.41571
pair_coeff 2 38 lj/cut 0.00238754 3.41571
pair_coeff 2 10
15 lj/cut 0.00238754 3.41571
pair_coeff 3 49 lj/cut 0.00238754 3.41571
pair_coeff 3 11
15 lj/cut 0.00238754 3.41571
pair_coeff 4 510 lj/cut 0.00238754 3.41571
pair_coeff 4 12
15 lj/cut 0.00238754 3.41571
pair_coeff 5 611 lj/cut 0.00238754 3.41571
pair_coeff 5 13
15 lj/cut 0.00238754 3.41571
pair_coeff 6 712 lj/cut 0.00238754 3.41571
pair_coeff 6 14
15 lj/cut 0.00238754 3.41571
pair_coeff 7 813 lj/cut 0.00238754 3.41571
pair_coeff 7 15 lj/cut 0.00238754 3.41571
pair_coeff 8 9
14 lj/cut 0.00238754 3.41571
pair_coeff 9 1015 lj/cut 0.00238754 3.41571
pair_coeff 10 11
15 lj/cut 0.00238754 3.41571
pair_coeff 11 1215 lj/cut 0.00238754 3.41571
pair_coeff 12 13
15 lj/cut 0.00238754 3.41571
pair_coeff 13 14*15 lj/cut 0.00238754 3.41571
pair_coeff 14 15 lj/cut 0.00238754 3.41571

neighbor 2 bin
timestep 0.0005

thermo_style multi
thermo 20

fixing the botttom atoms except the center one

fix 3 bottomm setforce 0.0 0.0 0.0

displacing the top atoms

fix 4 pull move linear 0.0 0.0 10.0 units box

compute 1 all pe/atom pair
compute 2 all pair lj/cut
fix 5 all ave/time 20 1 20 c_2 file paircompute.d mode scalar

dump 2 all atom 20 dump.pull

dump 3 all custom 10 dump.peatom c_1

run_style verlet
run 15000

Could be anything. Pulling too fast, pulling the wrong
atoms, etc. You will have to debug what is going on,
no one else is likely to do it.

Steve