Dear LAMMPS users ,
I am looking for Y-junction carbon nanotube coordinates for my simulations in LAMMPS.
Can you please let me know where I can find it ?
Thanks for your attention .
Best ,
saeed .
I am told that real nanotube junctions should have some curvature
near the junction as the carbon atoms near the junction adjust their
positions to remain well connected with their neighbors. So it would
not look exactly like the union of three ideal cylinders. It would
look smoother and rounder than that. (The same applies to
nanotube-graphene junctions).
If you don't care about this detail. If you are using moltemplate
and are willing to put up with it's limitations (no explicit bonds
connecting nearby carbons), then it is certainly possible to define a
nanotube, make 3 copies of it, (using rot() and move() commands to
move them into position), and then use "delete" commands to get rid of
the atoms in the overlapping volume. (Depending on the pair_style you
are using, you probably don't need explicit bonds in any case.)
Presumably, after you have built the initial structure, you could
then minimize the energy of the system (using pair_style AIREBO or
something similar) and/or run a short NVT simulation at reasonably
high temperature to relax the atoms, and generate a more smooth,
realistic-looking junction.
All of this (moving the nanotubes into position, and deleting the
correct atoms), currently requires iteratively running "moltemplate
-vmd system.lt", over and over again. Moltemplate does not have a
graphical user interface. So you must make changes to your
"system.lt" file and run "moltemplate -vmd system.lt" again to see if
it did what you expected (with VMD installed). You can even use
chiral tubes, if you don't mind manually deleting extra carbon atoms
at the (now jagged) ends of the tubes. It's kind of a pain, but in
principle, you can do all of it.
If it helps, regarding the force-field, here's a link to a
simulation of nanotubes (from the lammps web site, not built with
moltemplate), where they used the AIREBO pair style to model the
carbon-carbon interactions:
http://lammps.sandia.gov/images/cnt1.jpg
http://lammps.sandia.gov/images/cnt2.jpg
http://scitation.aip.org/content/aip/journal/jcp/134/20/10.1063/1.3594197?showFTTab=true&containerItemId=content/aip/journal/jcp
http://lammps.sandia.gov/pictures.html
Good luck
Andrew
Dear Andrew ,
Thanks for your kind help . I will do that .
Best regards ,
Saeed.