Hello,

I submitted a request called “Thermal Conductivity - Green-kubo Argon Example” and tried to cancel my request with the link provided because I figured out what was the issue. Now I would like to ask why is this method not to work properly when trying to find the thermal conductivity of Aluminum. I utilized a eam potential from NIST and changed the units and conversion variables appropriately and I’m getting an output of 13.45 W/mK @ 20 C when it should be much higher. Are there parameters that need to be altered? Below is the script that I’m using.

Thanks,

# Sample LAMMPS input script for thermal conductivity of solid Ar

#units real

units metal

variable T equal 293.15

variable V equal vol

#variable dt equal 4.0

variable dt equal 0.004

variable p equal 200 # correlation length

variable s equal 10 # sample interval

variable d equal $p*$s # dump interval

# convert from LAMMPS real units to SI

variable kB equal 1.3806504e-23 # [J/K] Boltzmann

#variable kCal2J equal 4186.0/6.02214e23

#variable A2m equal 1.0e-10

#variable fs2s equal 1.0e-15

#variable convert equal {kCal2J}*{kCal2J}/{fs2s}/{A2m}

variable eV2J equal 1.602176565e-19 #[J]

variable A2m equal 1.0e-10

variable ps2s equal 1.0e-12

variable convert equal {eV2J}*{eV2J}/{ps2s}/{A2m}

# setup problem

dimension 3

boundary p p p

#lattice fcc 5.376 orient x 1 0 0 orient y 0 1 0 orient z 0 0 1

lattice fcc 4.0 orient x 1 0 0 orient y 0 1 0 orient z 0 0 1

region box block 0 4 0 4 0 4

create_box 1 box

create_atoms 1 box

#mass 1 39.948

#pair_style lj/cut 13.0

#pair_coeff * * 0.2381 3.405

pair_style eam/alloy

pair_coeff * * Al99.eam.alloy Al

timestep ${dt}

thermo $d

# equilibration and thermalization

velocity all create $T 102486 mom yes rot yes dist gaussian

fix NVT all nvt temp $T $T 0.01 drag 0.2

run 80000

# thermal conductivity calculation, switch to NVE if desired

#unfix NVT

#fix NVE all nve

reset_timestep 0

dump 1 all atom 1000 dump.output

compute myKE all ke/atom

compute myPE all pe/atom

compute myStress all stress/atom NULL virial

compute flux all heat/flux myKE myPE myStress

variable Jx equal c_flux[1]/vol

variable Jy equal c_flux[2]/vol

variable Jz equal c_flux[3]/vol

fix JJ all ave/correlate $s $p d &
c_flux[1] c_flux[2] c_flux[3] type auto file J0Jt.dat ave running
variable scale equal {convert}/${kB}/$T/$T/$V*s*{dt}

variable k11 equal trap(f_JJ[3])*{scale}
variable k22 equal trap(f_JJ[4])*{scale}
variable k33 equal trap(f_JJ[5])*${scale}

thermo_style custom step temp density v_Jx v_Jy v_Jz v_k11 v_k22 v_k33

run 100000

variable k equal (v_k11+v_k22+v_k33)/3.0

variable ndens equal count(all)/vol

print “average conductivity: $k[W/mK] @ T K, {ndens} /A^3”