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[lammps-users] Spatial temperature distribution
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[lammps-users] Spatial temperature distribution

From: Nader Ameli <nader.mechanic@...24...>
Date: Wed, 11 Apr 2018 15:04:53 +0900

Dear LAMMPS users;


I am trying to achieve to the spatial temperature distribution (color coded visualization for the temperature of each atom) for nanometric machining. I have done this in 2 ways.

Firstly, I used kinetic energy:

compute keatom mobile ke/atom

fix fkeatom mobile ave/atom 50 4 $n c_keatom

variable  kb equal 1.3806504e-23 #Boltzmann const

variable avoqadro equal 6.0221409e+23 #Avoqadro const

variable tempatom atom "293+(2/3)*(1/v_kb)*f_fkeatom*(1/v_avoqadro)*(1/1000)*(10000)"

dump endis mobile custom $n endis/endis.$f.* x y z f_fkeatom c_keatom v_tempatom


The initial temperature of workpiece was 293K (which was expected). Nevertheless, by progressing the simulation, the workpiece temperature remained around 293K and no significant change occurred. Just like this, there was not any significant changes in kinetic energy of the workpiece.

Hence, I tried to use atom velocities as a new effort:

compute velatom1 mobile property/atom vx #Calculation of atoms velocity in X direction

compute velatom2 mobile property/atom vy #Calculation of atoms velocity in Y direction

compute velatom3 mobile property/atom vz #Calculation of atoms velocity in Z direction

variable totvelatom atom "sqrt((c_velatom1)^2+(c_velatom2)^2+(c_velatom3)^2)"

fix ftotvelatom mobile ave/atom 50 4 $n v_totvelatom

variable tempatom2 atom "293+(2/3)*(1/v_kb)*(1/2)*28.085*(f_ftotvelatom)^2 *(1/v_avoqadro)*(1/1000)*(10000)"       ## 28.085 is the mass of workpiece atom


Again, there was no significant change in the atom temperatures. Besides, another problem had arisen. The temperature range obtained from this new definition did not match with real temperature.

I have been struggling a lot with this and currently, I have no idea what I should do now. Just looking forward your valuable advices.