[gmx-users] What is the difference of using "system" and separating groups for "tc-grps"?

[ZHANG Cheng]

In the mdp file, I am using "tcoupl = v-rescale". 


Is there a difference between using "system" and separating groups for "tc-grps"?


e.g. 
; using "system":
tc-grps                  = system 
tau-t                    = 1.0 
ref-t                    = 335 



; using separating groups:
tc-grps                  = Protein W NA CL
tau-t                    = 1.0 1.0 1.0 1.0
ref-t                    = 335 335 335 335



Thank you!