[lammps-users] destroyed CNT using airebo

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1

Dear users,

I’m having trouble with the airebo potential. I want to simulate diffusion around a dynamic CNT.

However the CNT is destroyed when inserting LJ potentials of diffusing atoms. Temperature has no effect, here is my simplified input file:

I would have expected only little deformation of the tube, is there anything wrong with the input or are the results ok?

dimension 3

boundary p p p

atom_style bond

units metal

#(10,10 tube with 90 atoms around each end)

read_data run.data

mass 1 12

mass 2 16

group CNT type 1

group CH4 type 2

neighbour 2 bin

pair_style hybrid lj/cut 15 airebo 2 0 0

pair_coeff * * airebo CH.airebo C NULL

pair_coeff 1 2 lj/cut 0.005549 3.605

pair_coeff 2 2 lj/cut 0.01276 3.81

fix 1 all nvt 1400 1400 0.02 drag 0.5

timestep 0.0002

thermo_style multi

thermo 200

dump 1 all atom 200 result.lammpstrj

run 15000

thanks a lot in advance

Thomas

2

Is the CNT stable w/out the LJ atoms? If you're putting
the LJ atoms far from the CNT at low T, then I don't imagine
they affect the CNT immediately.

Steve

3

Dear Steve,

the CNT is stable without the LJ atoms if I leave the LJ term in airebo off, and is only strongly deformed when in closer contact to diffusing atoms.

Also, the temperature scaling (nvt) doesn't show any effect in the thermo file output (Temp = 0.0) if I run it without LJ atoms. Only with the atoms & CNT, the Temperatures are scaled correctly.

The airebo potential seems to have very little influence on the stability of the CNT, since the result of deformation of the CNT is almost similar to a run without any forces within the CNT.

So maybe the LJ potentials are just too strong compared to the airebo potential.

Thanks

Thomas