Some molecules with large ESP errors were not assigned off-center virtual sites. Chlorobenzene, for example, was found to have a large ESP error on the Cl atom just below the set threshold of 0.90 kcal/mol. However, the resulting liquid property predictions were not significantly affected (Table ). Methanol was another example of a molecule that was not assigned virtual sites despite having an ESP error of 1.50 kcal/mol, which is above the threshold. After performing the grid search it was found that the addition of virtual sites did not substantially reduce the ESP error of the oxygen atom by the required amount F change .