[phenixbb] Unmasking cavities

Hi After being through phenix.refine, I see in my hydrophobic core a big space (a few atoms wide) that is filled with strong negative difference density. I suspect the culprit is the bulk solvent mask, which is defined too tightly. The online manual mentions three parameters, but not what they do. solvent_radius, shrink_truncation_radius, grid_step_factor What *exactly* do they do? (I thought I'd elicit a contribution for the online docs this way :) Cheers phx