[gmx-users] gmx 4.6.6: rvdw == rcoulomb for Verlet lists

David Dotson dldotson at asu.edu
Thu Aug 7 07:12:01 CEST 2014

Thanks for the clear reply Justin. If *rvdw* does not change, that is 
enough for me.

Out of curiosity, what is the technical reason for the requirement 
"rcoulomb = rvdw", especially if rcoulomb is allowed to change during 
the simulation from tuning?


On 08/06/2014 06:28 PM, Justin Lemkul wrote:
> On 8/6/14, 3:56 PM, David Dotson wrote:
>> Good afternoon!
>> When using the Verlet lists cut-off scheme, grompp will throw an 
>> error if the
>> values for both *rcoulomb* and *rvdw* are not the same. However, when 
>> performing
>> md with *mdrun* and *-tunepme yes*, the coulomb cutoff will be 
>> adjusted along
>> with the pme grid to improve performance.
>> If the coulomb cutoff must equal that used for vdw, is this also 
>> adjusted during
>> the tuning? I ask because we are performing simulations with CHARMM36 
>> lipids,
>> and these have been shown to be sensitive to vdw cutoffs.
> rvdw is not adjusted, just rcoulomb.  The requirement for rcoulomb = 
> rvdw is for grompp processing.  It works the same way as rlist; it 
> gets tuned during the run with the Verlet scheme.
> -Justin

David L. Dotson
Center for Biological Physics
Arizona State University

Email: dldotson at asu.edu

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