[lammps-users] Carbon nanotube simulation

I am doing simulation of CNT. I am trying to do a simulation in which a single carbon atom with a certain velocity collides with an atom of CNT located at the center of the tube(length). However, the single atom does not move from its initial position irrespective of the velocity values.
The code I use:
units metal
boundary s p p
lattice hcp 1
atom_style atomic
read_data read10.cnt

pair_style airebo 2.5 1 1
pair_coeff * * CH.airebo C C C
group mobile type == 1
group fixed type == 2
group atom_pt type == 3

# Equilibrate
fix 1 mobile nvt 300.0 300.0 0.1
velocity fixed set 0.0 0.0 0.0
timestep 0.004
run 100

# Collision
velocity atom_pt set 0.0 -1.0 0.0
dump mydump all atom 100 dump.cnt
run 1000

Could anyone please suggest what could be wrong?


read10.cnt (12.4 KB)

If fixed and mobile are different groups, then
you are not time integrating the fixed atom. You
need a fix foo fixed nve for it.


The group ‘fixed’ is the group of all atoms that should remain with zero velocity. This fixed group is the group of atoms along the bottom edge of the tube(length) whereas the group atom_pt is a group of single atom, an atom which does not belong to CNT and I am trying to move this atom so that it collides with one of the CNT atoms.
So I applied fix nve to the group atom_pt, but the single atom does not move in y-direction (expected,since I’ve given velocity only in this direction), instead it goes in a different way. When I applied more velocity(in Y) it moves around the tube just like a satellite moving around a planet.
What I am really looking for is a collision b/w the two atoms.


Your explanation is confusing to me, but the rule is simple. If you
want an atom to move, you must time integrate it. It will not
move if you do not time integrate it. Whether or not you have
given an atom a velocity does not change this rule.