Comparison between vdW-DF and LJ potential

GROMACS version: 2021.2
GROMACS modification: No
Hi there, I am very new to GROMACS and work with ab-initio calculations. It seems I need to compare the interaction energy obtained by DFT (Done with Psi4 and Turbomole) and LJ potentials by Force Field methods. The systems are small molecular dimers.
Any help on how to do that in GROMACS?