[gmx-users] Temperature coupling groups

[Andreas Kukol]

Currently I do simulations with the following temperature coupling groups:

tcoupl                   = Berendsen
tc-grps                  = POPC Protein SOL Cl
tau-t                    = 0.1 0.1 0.1 0.1
ref-t                    = 300 300 300 300

How can I treat solvent (SOL) and Chloride (Cl) as one group and couple them  together to the 300K heatbath ? Simply removing Cl gives an error message.

Many thanks
Andreas