Since several people have asked me for code, I now realize that I've contributed my bit to the confusion over names of various surface definitions. To clear things up there is an excellent online article which covers the history of various molecular surface definitions that I highly recommend:
www.netsci.org/Science/Compchem/feature14e.html Mainly there are two related surface definitions: (a) solvent-accessible surface (b) molecular surface = contact surface + reentrant surface "solvent-excluded volume" has been defined using both of the above. Both (a) and (b) reduce to the same VDW surface when the solvent probe is zero. There are also a number of smooth approximations to these definitions and others. Richard Gillilan MacCHESS
