About energy groups in dihedral energies

GROMACS version: 2019.4
GROMACS modification: Plumed patched

How can I get torsion energies of certain dihedrals? I found that with energy groups settings, there are still only “Proper Dih.” and “Improper Dih.” output, which are the sum of all such torsion energies.

You could do this by extracting coordinates from the trajectory with trjconv and making a matching .tpr file with convert-tpr, then recompute the energies with mdrun -rerun but by definition, the dihedral energy for a single dihedral can be directly computed from its parameters. Force fields are parametrized against the potential energy of a molecule as a function of the dihedral angle(s) so writing out this term (which will just be a cosine or Fourier series, depending on which force field you’re using) is not really meaningful.