How to calculate the vdW energy when using the AIREBO?

Hi,

I use AIREBO potential to describe the interaction in a double walled
carbon nanotubes. But the evdwl is equal to pe in the output file. I
hope to obtain the vdW interaction energy between outer and inner CNT
only. How should I do?

Thanks,

Wan.

Hi,

I use AIREBO potential to describe the interaction in a double walled carbon
nanotubes. But the evdwl is equal to pe in the output file. I hope to obtain
the vdW interaction energy between outer and inner CNT only. How should I
do?

LAMMPS doesn't have an easy way to break down and store the individual
energy components of the AIREBO potential.

the most straightforward way that i can think of would be to record
your trajectory at sufficient intervals and then use the rerun feature
while using now pair_style lj/cut with suitably chosen parameters,
either via compute group/group or by assigning different atom types
for the atoms in each CNT and then setting all epsilon parameters to
zero except for the interactions between the two different types
representing the two different CNTs.

if you need to compute single point energies in a loop, you might be
able to do this by switching back and fourth between different pair
styles and parameter sets an then just using "run 0" to recompute the
energies.

there may be other ways (e.g. using a hybrid pair style or changing
how the airebo pair style tallies energies), but which is applicable
and how much effort it would take depends on your specific needs and
programming/scripting skills.

axel.