Dear Users,
The following input file is the KAPPA example provided by LAMMPS. In the last part, there is a variable “temp”. In computing the “temp” in uses “c_ke/1.5”. My question is that, why we divide the computed 'ke" to 1.5?
Thank you for your help in advance.
Best,
Ali
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