Dear all,
I want to add a viscous force in my simulation about ionization collisions, and I wish it only affect fast atoms with kinetic energy larger than 10eV. I only know I can assign these fast atoms in a group and then add a viscous force to this group, by something like:
compute keg all ke/atom
compute 2 all reduce sum c_keg
thermo 1
thermo_style custom step temp c_pkaTemp lx ly lz ke c_2
…
Run 0
variable Cufast atom “c_keg >= 10.0”
group fastCu variable Cufast
fix 4 fastCu viscous 0.3
However, this assignment is needed to be done after every steps, since the members of the fast atoms is varying in dynamic process. A loop “ group defined — fix viscous – run 1 — unfix viscous — group delete — “ can achieve this, but it cause a redundant and discontinuous thermo outputs. Maybe there is a more convenient way to achieve this via lammps command? Please inform me about it.