For geometry optimizations and Hessian calculations (energy 2nd-derivatives) the Generalized Born solvation model is used.
Poisson-Boltzmann Surface Area (PBSA)
The solvent energies (W) for minima found with the GB solvation model are corrected with the more accurate Poisson Boltzmann Surface Area (PBSA) method.
Explicit water molecules
For cases where particular water molecules in the binding site participate directly in the protein-ligand binding.