Re: [ESPResSo] Coulomb interactions 1D 3D

[Olaf Lenz]

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Hello!

Ivo Kabadshow wrote:
> I would assume that all particles have to be enclosed in the
> simulation-box (box_l box_l box_l). But the file holds particles with
> coordinates larger than l_box.

I have just started an FAQ for ESPResSo that contains an answer to your
question:

        http://espressowiki.mpip-mainz.mpg.de/wiki/index.php/FAQ

> What is the purpose of the first two particles with charge 0.0?

The script is part of the testsuite, that is intended to test all the
features of ESPResSo, and not as a comprehensive sample script. I
haven't created the test case, but I suppose that the reason for these
particles is to test whether the mmm1d algorithm can also handle
non-charged particles, i.e. whether it ignores it or not.

> What is the influence of the p3m parameter "cao"? I couldn't find any
> information.

The CAO parameter is the "charge assignment order". All parameters of
the P3M algorithm are described in the respective publications. For a
comprehensive description of the P3M algorithm, you should probably read

M. Deserno and C. Holm. "How to mesh up Ewald sums. I. A theoretical and
numerical comparison of various particle mesh routines". J. Chem. Phys.
109(7678), 1998.

and

M. Deserno and C. Holm. "How to mesh up Ewald sums. II. An accurate
error estimate for the particle-particle-particle-mesh algorithm". J.
Chem. Phys. 109(7694), 1998.

Best regards

        Olaf
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