Incorrect Temperature distribution using fix ave/spatial command for doped graphene

Hello all,

I am stuck with a basic error and can’t seem to find out a way out of it. Will be nice if anyone of you can help.

I performed equilibriation of two graphene sheets, one pure and the other doped (10%with C-14). After equilibriation, I created restart files and then started thermal conductivity calculations using “fix thermal” command for both of the cases for 8ns timestep.

In the last 1ns, I used “fix ave/spatial” to average the bin values over timescales and they were written to a file. Then when I am plotting the “Temp vs x” graphs, an inverted V shape plot (supposedly the correct shape) is coming for the pure graphenes but there is a lot of scatter in the “T vs x” plots for doped cases, which is incorrect. I ran this for a few lengths of graphenes, and in all the cases, the T vs x plots in cased of the doped graphenes came out to be incorrect.

I dont understand why this is happening. The only difference between the 2 cases are the data.graphene files. Or else I am using the same input script. Can anybody please help me sort this problem out? Thank You.

My input file (also attached) is as follows:

#Thermal Conductivity of Graphene Using Tersoff potential
read_restart equil.restart2

pair_style tersoff

pair_coeff * * SiC.tersoff C C
group Carbon type 1
log log.thermal

variable t equal 150000

thermo $t
fix NVT all nvt temp 300.0 300.0 0.1

compute ke Carbon ke/atom

variable temperature atom c_ke/(1.5*8.617e-5)
fix thermal all thermal/conductivity 300 x 100

thermo_style custom step temp pe ke etotal press lx ly lz f_thermal
run 7000000
write_restart equil.restart3

fix TEP all ave/spatial 1 100 100 x lower 3 v_temperature file temp.graphenedoped20 units box

run 1000000
write_restart equil.restart4

The output (log.thermal)is also attached below.


SiC.tersoff (1.53 KB)

equil.restart2 (283 KB)

in.graphenethermal (725 Bytes)

log.thermal (9.27 KB)

Have you visualized the results, have you dumped the
velocities yourself and verified that the temperature
profile is correct? It is unlikely that fix ave/spatial
is doing anything wrong, but you can check the results