add input for controlling a wall for a slab

# 3d Lennard-Jones melt, thermostatted by fix controller

units           lj

atom_style      atomic

boundary        p p m

processors      * * 1

lattice         fcc 0.8442

region          box block 0 10 0 10 -4 14

region          slab block 0 10 0 10 0 10

create_box      1 box

create_atoms    1 region slab

mass            1 1.0

velocity        all create 1.44 87287 loop geom

pair_style      lj/cut 2.5

pair_coeff      1 1 1.0 1.0 2.5

neighbor        0.3 bin

neigh_modify    delay 2 every 2 check yes

fix             1 all nve

fix             3 all langevin 1.5 1.5 0.5 412513

variable        zhi internal $(10.5*zlat)

variable        kwall equal 20.0

fix             2 all wall/harmonic zlo -0.5 ${kwall} 0.0 2.5 zhi v_zhi ${kwall} 0.0 2.5

variable        pzz equal pzz

fix             ave all ave/time 10 10 100 v_pzz

# equilibrate

thermo_style    custom  step temp pxx pyy pzz f_ave v_zhi

thermo           500

run             2500

# use time averaged pressure for control

#fix             10 all controller 100 -0.05 20.0 0.0 0.0 f_ave 1.5 zhi

# use instantaneous pressure for control

fix             10 all controller 100 -0.05 50.0 0.0 0.0 v_pzz 1.5 zhi

# run with controller

run             5000