[gmx-users] Re:The effect of coulomb-modifier and vdw-modifier in Verlet cutoff scheme

[Bin Liu]

Dear Mark,

Could you elaborate on your answer? In my group cutoff scheme, I used

ns_type         = grid          ; search neighboring grid cels
nstlist         = 5                 ; 10 fs
rlist           = 1.3           ; short-range neighborlist cutoff (in nm)
rcoulomb        = 1.3           ; short-range electrostatic cutoff (in nm)
rvdw            = 1.0           ; short-range van der Waals cutoff (in nm)
vdwtype         = Shift
rvdw_switch     = 0.9

What is the advantage of turning on coulomb-modifier and vdw-modifier in
terms of physical or chemical accuracy of simulations? Thanks.

Bin



Those modifiers shift only the potential, as manual 7.3 points out. So the
forces and sampling are unaffected, so it does not surprise me that APL is
unaffected by the use of such a shift. If your group cutoff scheme was
unbuffered (rlist <= max(rcoulcomb,rvdw) and nstlist > 1), then if the
observed difference is significant, then that could be the reason.