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lammps/examples/KAPPA/in.langevin
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# sample LAMMPS input script for thermal conductivity of liquid LJ
# thermostatting 2 regions via fix langevin
# settings
variable x equal 10
variable y equal 10
variable z equal 20
variable rho equal 0.6
variable t equal 1.35
variable rc equal 2.5
variable tlo equal 1.0
variable thi equal 1.70
#variable rho equal 0.85
#variable t equal 0.7
#variable rc equal 3.0
#variable tlo equal 0.3
#variable thi equal 1.0
# setup problem
units lj
atom_style atomic
lattice fcc ${rho}
region box block 0 $x 0 $y 0 $z
create_box 1 box
create_atoms 1 box
mass 1 1.0
velocity all create $t 87287
pair_style lj/cut ${rc}
pair_coeff 1 1 1.0 1.0
neighbor 0.3 bin
neigh_modify delay 0 every 1
# heat layers
region hot block INF INF INF INF 0 1
region cold block INF INF INF INF 10 11
compute Thot all temp/region hot
compute Tcold all temp/region cold
# 1st equilibration run
fix 1 all nvt temp $t $t 0.5
thermo 100
run 1000
velocity all scale $t
unfix 1
# 2nd equilibration run
fix 1 all nve
fix hot all langevin ${thi} ${thi} 1.0 59804 tally yes
fix cold all langevin ${tlo} ${tlo} 1.0 287859 tally yes
fix_modify hot temp Thot
fix_modify cold temp Tcold
variable tdiff equal c_Thot-c_Tcold
thermo_style custom step temp c_Thot c_Tcold f_hot f_cold v_tdiff
thermo 1000
run 10000
# thermal conductivity calculation
# reset langevin thermostats to zero energy accumulation
compute ke all ke/atom
variable temp atom c_ke/1.5
fix hot all langevin ${thi} ${thi} 1.0 59804 tally yes
fix cold all langevin ${tlo} ${tlo} 1.0 287859 tally yes
fix_modify hot temp Thot
fix_modify cold temp Tcold
fix ave all ave/time 10 100 1000 v_tdiff ave running
thermo_style custom step temp c_Thot c_Tcold f_hot f_cold v_tdiff f_ave
fix 2 all ave/spatial 10 100 1000 z lower 0.05 v_temp &
file profile.langevin units reduced
run 20000
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