Fixing More Than 32 Particles as Harmonic Springs in LAMMPS

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1

Dear LAMMPS-Users,

Good morning. I would like to fix a number of particles in my system as harmonic springs via the fix spring command with the tether keyword, but I need more than 32 groups. I am limited by cell size and must have a minimum of 64 cells. There is 1 harmonic particle per cell, which needs to be declared explicitly to fix it to its current position. Therefore, I would need:

fix ID groupID spring tether k x1 y1 z1 R0
…
fix ID groupID spring tether k xN yN zN R0

in order to fix each particle in each cell to its current position. Is there an efficient way to get around this? I have read the manual, but perhaps more experienced users can suggest a trick of the trade.

Thank you, and have a great day.
Christin

2

Dear LAMMPS-Users,

Good morning. I would like to fix a number of particles in my system as
harmonic springs via the fix spring command with the tether keyword, but I
need more than 32 groups. I am limited by cell size and must have a minimum
of 64 cells. There is 1 harmonic particle per cell, which needs to be
declared explicitly to fix it to its current position. Therefore, I would

move the atoms where you need then and then use
fix spring/self
this way you need only one group.

axel.