Hi Wade, The problem with 1tcr.phi is that it is not the right type of file. It is a text file that gives electric field at each atom position. You can open it in a text editor and see, but Chimera cannot do anything with that file. The DelPhi potential files read by Chimera (*.phi) are binary files that contain a rectangular grid of electric potential values. It looks like the Honig lab server does not provide those. Tom