Dear Bo,
Check the thread below:
http://sourceforge.net/mailarchive/forum.php?thread_name=5da157840911110753m79bb1c9ascca5ac776f2ddc1d%40mail.gmail.com&forum_name=lammps-users
German had posted these files earlier.
Using them, one can include the coulombic interaction terms to calculate heat flux.
Best,
Mario