in relax.lmp

# Annealing, cooling, and final minimization of an elemental polycrystal
# The structure is annealed at the target temperature, cooled to near 0 K,
# and then relaxed by conjugate-gradient minimization.

units           metal
atom_style      atomic
boundary        p p p
read_data       70+5.lmp

# Atomic mass and interatomic potential (elemental Al case shown here)
mass            1 26.98
pair_style      eam/alloy
pair_coeff      * * AlCu.eam Al

# Time integration settings
timestep        0.001
variable        T_anneal      equal 373.2
variable        T_cool_start  equal ${T_anneal}
variable        T_cool_end    equal 0.1
variable        CoolingRate   equal 3

# High-temperature annealing
fix             anneal all npt temp ${T_anneal} ${T_anneal} 0.1 iso 0 0 1.0
dump            anneal_dump all custom 1000 elemental_polycrystal_anneal.lammpstrj id type x y z
thermo          1000
thermo_style    custom step temp press vol lx ly lz
run             250000
unfix           anneal

# Controlled cooling to near 0 K
fix             cool all npt temp ${T_cool_start} ${T_cool_end} 2.0 iso 0 0 1.0
dump            cool_dump all custom 1000 elemental_polycrystal_cooling.lammpstrj id type x y z
thermo          1000
thermo_style    custom step temp press vol lx ly lz
run             124360
unfix           cool
undump          anneal_dump
undump          cool_dump

# Final static relaxation
min_style       cg
min_modify      dmax 0.1
minimize        0 1.0e-12 10000 100000
write_data      elemental_polycrystal_annealed.data
print           "Simulation finished. Final minimized structure written to elemental_polycrystal_annealed.data."

# Example run command:
# mpiexec -np 4 lmp -in in.lmp -pk omp 4 -sf omp