[lammps-users] atoms moving out


I had used the following code for an MD simulation on carbon nanotubes. The coordinates of all the atoms are specified using a file called coordinates. I did not specify any information about the bonds between atoms. When i run this program, the structure is getting deformed in a random manner and they are not vibratiing about their mean positions and as a result the originial structure is not retained during the simulation. Can u please tell me what should i do to make it work??

units real
dimension 3
boundary s s p

atom_style atomic

pair_style airebo 3.0

read_data coordinatesofcnt.txt

pair_coeff * * CH.airebo C

#read data command for coordinates of atoms

#create velocities on all atoms, using T = 300, with a

velocity all create 300.0 873586443 dist gaussian

fix 1 all nvt 300 300 100 drag 0.4

#output of varaibles
timestep 0.25

dump 1 all atom 50 temp.opt

run 25000

The following quote the document of LAMMPS online. So you should be careful using “real” units.

The CH.airebo potential file provided with LAMMPS (see the potentials directory) is parameterized for metal units. You can use the AIREBO potential with any LAMMPS units, but you would need to create your own AIREBO potential file with coefficients listed in the appropriate units if your simulation doesn’t use “metal” units.