[gmx-users] Re: Cutoff: PME vs Shift

Dr. Vitaly Chaban vvchaban at gmail.com
Sat Jan 12 12:16:11 CET 2013

Hi Juliette N. -

In general -- yes, you are right. Your system probably has tiny point charges...

I would also compare electrostatics terms directly, but they are
unlikely to differ. Or perhaps even better,  look at the Coul.-recip.
term. If it small as compared to  LJ-(SR) than it is fine to switch to
simpler electrostatics treatment.

> Hello all,
> I am trying to compare PME and shift electrostatics methods for my
> hydrocarbon system. In both cases rlist               =  1.35 , but in case
> of PME rcoulomb            =  1.35 while for shift **
> rcoulomb            =  1.1. I see no significant change (less than 1%) in
> total system potential, however I would like to know if I can conclude that
> electrostatic energy is insensitive to cutoff distance of rcoulomb as a
> result of change from 1.1 (shift) to 1.35 (PME)?*
> *
> Is this a correct interpretation?

Dr. Vitaly V. Chaban
MEMPHYS - Center for Biomembrane Physics
Department of Physics, Chemistry and Pharmacy
University of Southern Denmark
Campusvej 55, 5230 Odense M, Denmark

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