I notice that the thermal conductivity of copper at 85K is about 500W/mK, but why I got the result using fix thermal/conductivity is only 2W/mK,which is so small.
The input script is in the following:
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# MD simulation of Cu thermal conductivity at 85.8798143251905K
# Initialization
units metal
dimension 3
newton on
boundary p p p
atom_style atomic
neighbor 2.0 bin
neigh_modify check yes
lattice fcc 3.61070147794558
region box block -4 4 -4 4 -4 4 units lattice
create_box 1 box
create_atoms 1 box
region up1 block INF INF INF INF -0.5 -0.25 units lattice
region up2 block INF INF INF INF 0.5 0.75 units lattice
region up union 2 up1 up2
group up region up
region down1 block INF INF INF INF -3.5 -3.25 units lattice
region down2 block INF INF INF INF 3.5 3.75 units lattice
region down union 2 down1 down2
group down region down
mass 1 63.5
velocity all create 85.8798143251905 458127641 mom yes rot yes dist gaussian units box
# EAM potential
pair_style eam
pair_coeff 1 1 Cu_u3.eam # EAM parameters for Cu-Cu
fix temp all temp/berendsen 85.8798143251905 85.8798143251905 0.1
fix nve all nve
compute ke all ke/atom
variable temp atom c_ke/(1.58.617343e-5)
fix temp_profile all ave/spatial 1 100000 100000 z lower 0.25 v_temp file temp.profile units lattice
compute up_temp all temp/region up
compute down_temp all temp/region down
variable delta_temp equal c_up_temp-c_down_temp
fix delta_out all ave/time 1 100000 100000 v_delta_temp file delta_temp.dat
thermo_style custom step temp etotal vol
thermo_modify lost warn
thermo 1000
dump atom all atom 100000 dump.atom
# Run
timestep 0.001
run 100001
unfix temp
fix heat_swap all thermal/conductivity 10 z 32
fix e_exchange all ave/time 10 10000 100000 f_heat_swap file e_exchange.dat
variable thermal_conductivity equal f_e_exchange/(0.00110.04.0f_delta_out)1.60217646e-19/1.0e-10/1.0e-126.0/8.0
fix thermal_conductivity_out all ave/time 100000 1 100000 v_thermal_conductivity file thermal_conductivity.dat
# Run
run 10000000
Xiaoliang Zhang
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The main heat carrier in Cu is electron. You’re missing the major part by using MD.
Tengfei
Copper is a metal. Electrons are the dominant heat carriers in metals. Your simulations only calculate phononic (vibrational) part of the thermal conductivity. Thats the problem.
OK, MD underestimates the TC of Cu so much, but why Sarkar used MD to simulate thermal conductivity of Ar-Cu nanofluids. Is his result reliable? Does it make sense?
Xiaoliang Zhang
— 10年4月15日，周四, Vikas Varshney <vv0210@…24…> 写道：
The argument of Sarkar’s paper is that the presence of Cu particle leads to a increased motion of the liquid atoms, which results in a higher K. It is not the high K of Cu that leads to the enhancement. It is the vibration not the electrons that transport heat between Cu and LJ liquid. Ignoring electron’s effect is OK from my point of view. There are also a lot of debate on the mechanism of K enhancement of nanofluid. But Sarkar’s paper make sense to me for that specific case.
Tengfei