Dear all, how can I manage to put a certain number of water molecules in a box? I tried the genbox -nmol option with -ci spc216.gro, but it didn't work out due to "more than one residue". Can I convert the spc216.gro file so that it'll contain only one residue (and how) or is there a better way? I need to have the same number of molecules in a box, if I want to do free energy calculations, right? Thanks in advance for any support! Bye, Martin