[lammps-users] Fix_heat

Dear Lammps users,

I want to supply some heat to one portion of my simulation domain and want to take out heat from the other portion. I am using fix_heat given in the lammps documents like

fix 3 upper heat 1 10.0
fix 4 lower heat 1 -1.0

but it gives error as Illegal fix heat attempt. but when I am removing the heat extraction (-1), then it run fine. Please write the where is the error


If you’re putting in more heat than you’re taking out, then you’re system will continuously get hotter. So you probably want something more like:

fix 3 qin heat 1 1.0
fix 4 qout heat 1 -1.0

Even so, I don’t see why you’d get an error message with the input commands that you used.

Are your “upper” and “lower” groups defined? Are the fix IDs already used elsewhere?

If this doesn’t help, you might try posting your entire input script along with all of the output that you’re seeing. You might even send along your initial configuration data file if it is small.


As another user commented, this occurs when you are attempting
to take out so much heat that the KE goes negative.