Need assistance in Double wall carbon nanotube(DWCNT) simulation

Please always CC to the lammps
we have double walled CNT. so you should place the inner CNT as the type 1 and the outer CNT as type 2 in order to be able to create the LJ potential between inner and the outer tube.
I do it in this way, I import the coordinate of th two CNT in EXCEL and then add a column to each file with the corresponding number 1 and 2. then copy and paste it to the Notepad or datafile
Nanotube modeler does not create lammps datafile

Mehdi

Mr Mehdi,

I have tried for DWCNT have a structure of (10,0) as inner tube and (15,0) as outer tube. when i was simulate with input file which was sent by you. The inner and outer tubes were going apart during the relaxation. can you tell me what went wrong.

Mr Mehdi,

  I have tried for DWCNT have a structure of (10,0) as inner tube and (15,0)
as outer tube. when i was simulate with input file which was sent by you.
The inner and outer tubes were going apart during the relaxation. can you
tell me what went wrong.

there is not enough detail here and there is no copy of your input in
mailing list archives.
most likely your atoms were overlapping. i just build a system with
VMD and it looks as if the two nanotubes are *very* tight and thus
there is going to be quite a bit of potential energy between them.

axel.

p.s.: in case somebody is curious, here is the VMD script code to be
run with vmd -dispdev text -e thisscript.tcl

package require nanotube 1.5
package require topotools 1.4

# build 5nm long (10,0) CNT
nanotube -l 5 -n 10 -m 0
# and reset atom name/type
set sel1 [atomselect top all]
$sel1 set type C1

# build 5nm long (15,0) CNT
nanotube -l 5 -n 15 -m 0
# and reset atom name/type
set sel2 [atomselect top all]
$sel1 set type C2

# combine the two separate molecules into a single one
TopoTools::mergemols [list [$sel1 molid] [$sel2 molid]]
# and write out to a suitable data file w/o bond info
topo writelammpsdata dwcnt.data atomic

exit

Dr.Axel,

Here i am attaching input file and data file generated by the tcl script. I am getting the same problem of inner and outer tubes were going apart.

dwcnt.data (47.1 KB)

in.cnt (5.1 KB)

Dr.Axel,

Here i am attaching input file and data file generated by the tcl script. I
am getting the same problem of inner and outer tubes were going apart.

that by itself is not a problem but actually the proper physical
behavior of two nanotubes that are stuck together _this_ tightly.

however, there *is* a problem with how you specify your interactions.

your input has:

pair_style hybrid tersoff lj/cut 8.5
pair_coeff * * tersoff SiC.tersoff C C
pair_coeff 1 2 lj/cut 0.00239 3.4

which is flat out wrong, since you remove some manybody terms, but not
all and you do this in a very inconsistent way.

if you want to have two entities using manybody terms internally and
combine them via a LJ potential, each of them has to be treated as a
completely contained entity, which means you need two separate
manybody pair_coeff definitions. you can do this with:

pair_style hybrid tersoff tersoff lj/cut 8.5
pair_coeff * * tersoff 1 SiC.tersoff C NULL
pair_coeff * * tersoff 2 SiC.tersoff NULL C
pair_coeff 1 2 lj/cut 0.00239 3.4

mind you that will *still* push the two nanotubes apart, because that
is the physics of this model.

axel.

i try to simulate DWCNT, the Pair_coeff defined as below with the data file generated by Nanotube modeler, which i got from lammps user Mr.Mehdi.

CNT_data.xyz (120 KB)

in.cnt (5.1 KB)

i try to simulate DWCNT, the Pair_coeff defined as below with the data file
generated by Nanotube modeler, which i got from lammps user Mr.Mehdi.

pair_style hybrid tersoff tersoff lj/cut 8.5
pair_coeff * * tersoff 1 SiC.tersoff C NULL
pair_coeff * * tersoff 2 SiC.tersoff NULL C
pair_coeff 1 2 lj/cut 0.00239 3.4

i got the error message
ERROR: Incorrect args for pair coefficients (../pair_tersoff.cpp:274)

are you using a current version of LAMMPS? this works fine for me.

But when i tried with following Pair_coeff definition. its running and also
the two nanotubes not separated apart.

still, this input is wrong. it has been explained on this list many times why.

axel.

dear Thamarai,
Axel is correct.
you can not build any types of MWCNT as you want. the balanced vanderwales distance between them should be equal to 3.4A.
your model consist of a (10,0)/(15,0) Zigzaag DWCNT. that is wrong. take a look at the file which is attached for you. for Zigzga MWCNT the numbers should increase 9 steps. for example (10,0)/(19,0) DWCNT.
for Armachiar MWCNT they should be increased by 5 steps. for example (10,10)/(15,15)
then your model should be modified. the distance between the CNTs are wrong

take a look at the following paper which I attached.
"2009_Vibration analysis of multi-walled carbon nanotubes using a spring–mass_Georgantzinos"

2009_Vibration analysis of multi-walled carbon nanotubes using a spring–mass_Georgantzinos.pdf (1.6 MB)