Sorry for the over-simplicity before, what I meant is the scripts from LAMMPS mannual, as attached below.

I got different results for varying s (sample interval), I am thinking if it's due to the definition of {scale} in the lower part, if I modify this Ar case for Si with metal units.

(Forgive me, I am a completely new LAMMPS user. )

Thanks for giving any suggestions.

(http://lammps.sandia.gov/doc/compute_heat_flux.html)

```
# Sample LAMMPS input script for thermal conductivity of solid Ar
```

```
units real
variable T equal 70
variable V equal vol
variable dt equal 4.0
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}
```

```
# 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
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
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 10 drag 0.2
run 8000
```

```
# thermal conductivity calculation, switch to NVE if desired
```

```
#unfix NVT
#fix NVE all nve
```

```
reset_timestep 0
compute myKE all ke/atom
compute myPE all pe/atom
compute myStress all stress/atom 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 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"
```