[gmx-users] Parameters in PME

Janne Hirvi janne.hirvi at joensuu.fi
Tue Aug 2 11:46:20 CEST 2005


I am not specially familiar with the deepest theory of PME, but I have tried to
figure out the meaning of all relevant electrostatics run parameters in
However I haven't been able to find out how can I determine or discover
parameters similar to traditional Ewald summation given in all journals. I
think that all these parameters should be in usage also in PME excluding the
differences in reciprocal space (k-vectors and grid).

So I suppose that rcoulomb correspondes to the cut-off in real space, but what
is the cut-off in reciprocal space? Is it just this fourierspacing parameter
(or gridspacing) without any "real" cut-off?

Then there are these pme_order and ewald_rtol, which I suppose to affect to the
convergence, but how can I get the level of convergence with respect to a fully
converged Ewald sum? Do I need to simulate one with using as accurate
parameters (pme_order and ewald_rtol) as possible and then compare?

How about then something called the separation factor? Can someone tell me what
it is? I have tried to find it from the literature, but without any "luck".

So there is many hard questions for me and I hope some of you more experienced
users could help me to understand these things. Thanks for you all in advance.

Janne Hirvi

Janne Hirvi, MSc(Physical Chemistry), Researcher
University of Joensuu, Department of Chemistry, P.O.Box 111 80101 Joensuu, FI
Tel: +358 13 2513326 & +358 50 3474223
E-mail: Janne.Hirvi at joensuu.fi & hirvi at cc.joensuu.fi

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