[gmx-users] ewald_rtol

Justin A. Lemkul jalemkul at vt.edu
Mon Apr 16 19:44:09 CEST 2012

Andrew DeYoung wrote:
> Hi,
> Does the parameter ewald_rtol affect PME electrostatics (coulombtype = PME),
> or does ewald_rtol only affect Ewald electrostatics (coulombtype = Ewald)?
> In the manual description of the .mdp parameters
> (http://manual.gromacs.org/current/online/mdp_opt.html#el), it says in the
> Ewald section, "The relative accuracy of direct/reciprocal space is
> controlled by ewald_rtol."  Similarly, page 100 of the manual says, "The
> ewald_rtol parameter is the relative strength of the electrostatic
> interaction at the cut-off. Decreasing this gives you a more accurate direct
> sum, but a less accurate reciprocal sum."
> However, I do not see ewald_rtol specifically discussed in any of the manual
> sections on PME.  Does this mean that ewald_rtol is only relevant for the
> (normal, classical) Ewald sum electrostatics?

It is related to PME.


There are a number of other discussions about it in the list archive; I'd 
suggest you have a look.



Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080


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