[lammps-users] Does anyone have experience in thermal conductivity simulation of graphene sheet?

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1

Dear Steve and everyone,

Do you have any experience about the thermal conductivity simulation of graphene sheets?

Now I’m using Muller-Plathe method to simulate the thermal conductivity of the graphene sheet with the AIREBO potential, but my result is far away from the reported and experimental results. I simulated graphene sheets with several different sizes and found all of the thermal conductivity are around ~ 200W/K/m, which is 10~20 times smaller than the published result. I used the following input file to calculate the thermal conductivity:

********************************************************************

dimension 3
boundary p p p

units metal

atom_style molecular
read_restart res_0.7ns # restart file after 0.5ns NVT simulation and 0.2ns NVE simulation at 300K

pair_style airebo 3.0 1 1
pair_coeff * * CH.airebo C

timestep 0.001
velocity all create 300 1234567 dist gaussian
fix 2 all nve #perform constant NVE integration to update position and velocity for atoms in the group each timestep

thermo 1000
fix flux all thermal/conductivity 50 z 24
compute ke all ke/atom
variable temp atom c_ke[]/0.0001292355
fix 3 all ave/spatial 10 100 1000 z lower 3.0 v_temp file tmp.profile units box

dump ani all xyz 5000 graphtraj.xyz
dump_modify ani format “C %14.6g %14.6g %14.6g”

thermo 1000
thermo_style custom step ke pe etotal temp press f_flux

run 4000000

figures.doc (240 KB)

2

Looking at the graph I see that you have clearly driven the system past linear response. I don't know if that is enough to explain the poor agreement with the experimental value, but you should redo it with a less frequent swap and see.
Cheers,
Matt

Quoting Dongshan Wei <[email protected]...>:

3

Matt's advice is good. You're also getting a warning, which the
error page describes thusly:

Fix thermal/conductivity comes before fix ave/spatial
    The order of these 2 fixes in your input script is such that fix
thermal/conductivity comes first. If you are using fix ave/spatial to
measure the temperature profile induced by fix viscosity, then this
may cause a glitch in the profile since you are averaging immediately
after swaps have occurred. Flipping the order of the 2 fixes typically
helps.

Steve