Dear LAMMPS users
I am working on amorphous carbon simulations.
I want to compare several potentials’ performance on this material: REBO, AIREBO, LCBOP and TERSOFF.
First step is check energy conservation, so I did the following simple test:
Starting from an amorphous carbon structure at room temperature, I run a fix nve for 10 ps with every potentials and then check the total E conservation and the Temperature profile vs time - input file at the end.
I found out LCBOP, REBO and AIREBO don’t conserve total energy. On the other hand, TERSOFF works perfectly fine.
I’m aware of similar problems with AIREBO, according to other posts in the forum.
I decreased the timestep size from 0.1 fs down to 0.01 fs without significant improvement. I also did a test updating the neighbor list every step, no improvements.
REBO always shows a ~ 30 eV upward drift in the total energy after 10 ps, but LCBOP behaves just crazy.
My questions are:
1) Since E conservation in NVE is never perfect, REBO’s drift is acceptable for practical purposes?
2) Is somebody aware of any bug in these potentials? specially in LCBOP?
LAMMPS INPUT FILE for REBO
boundary p p p
read_restart RESTART_amorphous3.0gcc.105000 # starting amorphous carbon structure
pair_coeff * * CH.airebo C
fix 1 all nve
timestep 0.0001 # timestep of 0.1 fs
thermo_style custom time step pe ke etotal temp vol density
run 100000 # run for 10 ps
Thank you in advance
Carla de Tomas
Dept. of Physics and Engineering