The FCO-MBD method provides accurate dispersion energies and long-range correlation contributions to electronic density, making it a powerful vdW approach. Notably, this is achieved without empirical parameters, making the model fully self-contained. This underscores the importance of seamless treatment of long-range correlations in future DFAs. However, an open challenge remains: how to couple a vdW method like FCO-MBD with existing DFAs to avoid double-counting correlation effects at certain interatomic distances? The common approach of using a damping parameter introduces empirical adjustments that obscure the physical meaning of vdW energy . One solution could be using "dispersionless" DFAs , such as those proposed by Pernal et al. , or mixing HF exchange with PBE correlation . Another option is to base the range-separation parameter on density instead of energy, minimizing errors by fitting to high-accuracy ab initio densities, such as those from CCSD for small molecules.