cummulative energy of temp/rescale with spring/self?

thanks steve.
by "fix heat " I can’t get constant temperature gradient.
by "fix temp/rescale " command I get temperature gradient but I can’t obtain heat flux.
I think I use it correctly for exampel if I use “fix ID temp/rescale …” then I use “f_ID” for cummulative energy.

is it true?
if the wrong result caused by springs ?
how can I get correct result?

Most people apply fix heat (or fix temp/rescale) to mobile
atoms, not contstrained ones. So if you are applying them
to atoms also tethered by springs, maybe that is an issue.