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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@5439 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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2011-01-03 16:42:55 +00:00
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doc/compute_heat_flux.html
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@ -89,8 +89,8 @@ integral estimated, and the Green-Kubo formula above evaluated.
the autocorrelation. The trap() function in the
<A HREF = "variable.html">variable</A> command can calculate the integral.
</P>
<P>An an example LAMMPS input script for solid Ar is appended below.
The result should be: average conductivity ~0.29 in W/mK.
<P>An example LAMMPS input script for solid Ar is appended below. The
result should be: average conductivity ~0.29 in W/mK.
</P>
<HR>
@ -128,24 +128,29 @@ energy/area/time <A HREF = "units.html">units</A>
</P>
<HR>
<H4>Sample LAMMPS input script
</H4>
<PRE>atom_style atomic
units real
variable kB equal 1.3806504e-23 # [J/K] Boltzmann
variable kCal2J equal 4186.0/6.02214e23
<PRE># Sample LAMMPS input script for thermal conductivity of solid Ar
</PRE>
<PRE>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
variable p equal 200 # correlation length
variable s equal 10 # sample interval
variable d equal $p*$s # dump interval
</PRE>
<PRE># convert from LAMMPS real units to SI
</PRE>
<PRE>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}
</PRE>
<PRE># setup problem
</PRE>
<P># ---------------------------------------------------------
</P>
<PRE>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 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
@ -155,34 +160,35 @@ pair_coeff * * 0.2381 3.405
timestep ${dt}
thermo $d
</PRE>
<P># ------------- equilibration and thermalization ----------------
</P>
<PRE>velocity all create $T 102486 mom yes rot yes dist gaussian
fix NVT all nvt temp $T $T 10 drag 0.2
run 8000
<PRE># equilibration and thermalization
</PRE>
<P># -------------- flux calculation, switch to NVE if desired --------
</P>
<PRE>#unfix NVT
#fix NVE all nve
<PRE>velocity all create $T 102486 mom yes rot yes dist gaussian
fix NVT all nvt temp $T $T 10 drag 0.2
run 8000
</PRE>
<PRE>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 ${kCal2J}*${kCal2J}/${kB}/$T/$T/$V*$s*${dt}*1.0e25
variable k11 equal trap(f_JJ[3])*${scale}
variable k22 equal trap(f_JJ[4])*${scale}
variable k33 equal trap(f_JJ[5])*${scale}
<PRE># thermal conductivity calculation, switch to NVE if desired
</PRE>
<PRE>#unfix NVT
#fix NVE all nve
</PRE>
<PRE>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
print "average conductivity: $k [W/mK]"
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"
</PRE>
</HTML>