Fix wall/piston command

I’m trying to use the command fix wall/piston only on a group of atoms, but it does not seem to do anything to the data I’m using. This is the code I’m wrote

1. Initialisation

units metal
dimension 3
boundary s s s
atom_style atomic
timestep 0.001
neighbor 2.0 nsq

2. system definition

read_data datrec3k.lammps

group forced type 2
group boundary type 1
group relaxed type 3

3. simulation settings

pair_style rebo
pair_coeff * * CH.rebo C C C

fix freeze boundary setforce 0.0 0.0 0.0

fix pist forced wall/piston zlo pos 5 vel 0.0 units box

thermo 10
thermo_style custom step etotal fmax fnorm
thermo_modify norm yes

dump 1 all xyz 100000 dump-rec3kpiston.txt
dump_modify 1 element C C C

4. run the simulation

min_style fire
minimize 0.0 3.12e-4 1000000 10000000

I have try using it both with and without velocity, and using the ramp option. Non of these things seems to work.

The documentation of fix wall/piston explicitly states that it is not run during minimization.
So why should there be any effect in your calculation?