Subject: Electrostatic sums

From: Andrew Horsfield <[email-masked]>
Date: Wed, 2 Feb 2000 16:10:59 +0000 (GMT)

Hi,

I am attempting to solve Poisson's equation on an atom centered mesh (such
as is used in DMol). It is clear how to do this for a molecule. A solid
can be thought of as a periodically repeated molecule. So it is also
(almost) clear how to handle solids. The problem is the long ranged nature
of the Coulomb interaction.

I know how to use the Ewald summation technique for the monopole terms. Do
I need to use a corresponding technique for the dipole and quadrupole
terms, or can I just use a real space sum? For octupole and above it looks
to me like the potential decays fast enough with distance to guarantee
convergence using a simple real space summation. Is this correct?

Cheers,

Andrew

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