  Liquid states theories have emerged as a numerically efficient alternative to
costly molecular dynamics simulations of electron transfer reactions in
solution. In a recent paper [Chem. Sci., 2019, 10, 2130], we introduced the
framework to compute energy gap, free energy profile and reorganization free
energy using molecular density functional theory. However, this technique, as
other molecular liquid state theories, overestimates the bulk pressure of the
fluids. Because of the too high pressure, the predicted free energy is
dramatically exaggerated. Several attempts were made to fix this issue, either
based on simple a posteriori correction or by improving the description of the
liquid introducing bridge terms. By studying two model half reactions in water,
Cl -> Cl+ and Cl -> Cl-, we assess the correctness of these two types of
corrections to study electron transfer reactions. We found that a posteriori
corrections, because they violate the functional principle, lead to an
inconsistency in the definition of the reorganization free energy and should
not be used to study electron transfer reactions. The bridge approach, because
it is theoretically well grounded, is perfectly suitable for this type of
systems.
