[gmx-users] vsites with CHARMM force fields

[Ramon Crehuet Simon]

Dear all, 

I am simulating a system with CHARMM36m force field. Following the recommendations in the mailing list and the gromacs web page, I constrained only h-bonds (constraints = h-bonds). 

In that case, does it make sense to use virtual sites to allow 4fs time step? In other words, if vsites remove the fastest degrees of freedom, but we do not constrain bond distances, will a 4 fs time-step be stable? 

Thanks in advance, 

Ramon