Asking for an alternative to fix heat command.

Dear All,

I want to examine the decomposition of hexagonal boron nitride and on the fly of behavior decomposed particles by just constantly heating the upper non-thermostatted layer of the structure using fix heat command. The region that I used constantly moves to lower in the z direction to add the heat to the lower layers. As I understood from the documentation fix heat command adds non-translational kinetic energy by conserving their aggregate momentum. When the system starts to decompose I get “fix heat kinetic energy went negative” error. From my understanding using the fix heat command for such purpose is not correct. I am only interested in decomposition and the flight behaviour of decomposed and sputtered particles. By doing this my plan is to evaluate flight behavior and to calculate the mean free path of the sputtered particles.

I have installed two different versions of lammps (30 Oct 2019 and 5 May 2020) on two different workstations (using Ubuntu 18.04) to test the setup before I submit it to HPC. I have tried using different amounts of energy or different time steps for the test purposes. If I use smaller N steps like 1 or 10 for fix heat command, lammps gets stalled (CPUs are still busy but no output). If I use larger N steps like 1000 steps the simulation works well but I get fix heat kinetic energy went negative. I have attached the short version of my script(google drive link due to the size limit) and Snapshot of the last step when I get kinetic energy went negative error.(fix 7a target heat 1000 v_a_heat region heat was used with v_a_heat equal 11)

What kind of other command that I can use for this purpose, which I am not aware of.? I used fix ehex and fix ttm also but it did not work well either.

Thanks for your help in advance

Attached Files

Best Regards

Sakarya University

Dept. of Metallurgical and Materials Eng.