Heat flux autocorrellation function

GROMACS version: 2020
GROMACS modification: Yes/No

Hello,

I would like to use the Green-Kubo approach to calculate the thermal conductivity of a aqueous solution. As far as I know, Gromacs has built-in commands for velocity and current ATF but I failed to find a command to compute heat flux ATF.

Can anyone suggest how to get the heat flux ATF in Gromacs?

Any reply would be thankful!