[lammps-users] fix_heat

Here is my input and output, please suggest me about the error

units metal
dimension 3
boundary p p p
atom_style atomic
neighbor 2 bin
neigh_modify delay 5

create geometry

lattice fcc 4.08
region box block 0 12 0 20 -3 3
create_box 5 box
create_atoms 1 box
mass 1 196.7
mass 2 196.7
mass 3 196.7
mass 4 196.7
mass 5 196.7

LJ potentials

pair_style eam
pair_coeff * * ./Au_u3.eam

region 1 block INF INF INF 4 INF INF
group lower region 1
region 2 block INF INF 16 INF INF INF
group upper region 2
region 3 block INF INF 4 16 INF INF
group middle region 3

fix 1 upper heat 1 1.0
fix 2 lower heat 1 -1.0
fix 3 middle nve
timestep 0.001
run 10000
Lattice spacing in x,y,z = 4.08 4.08 4.08
Created orthogonal box = (0 0 -12.24) to (48.96 81.6 12.24)
1 by 17 by 1 processor grid
Created 5760 atoms
1296 atoms in group lower
1152 atoms in group upper
3600 atoms in group middle
Setting atom values …
1296 settings made for type
Setting atom values …
1152 settings made for type
Setting up run …
Memory usage per processor = 1.91138 Mbytes
Step Temp E_pair E_mol TotEng Press
0 0 -22636.8 0 -22636.8 0.022463201
ERROR: Illegal fix heat attempt

Regards,

Navin