Subject: Integral meshes for LCAO codes

From: Andrew Horsfield <[email-masked]>
Date: Thu, 13 Jan 2000 12:04:33 +0000 (GMT)

Hi,

I am developing a numerical atomic orbital density functional code for
solids (Plato). I am using pseudo-potentials, so have often been able to
get away with using the FFT mesh as my integral mesh for integrals
involving the exchange and correlation potential. However, it is now clear
that as the basis set approaches completeness this approach fails
spectacularly (very deep ghost bands form). Increasing the mesh density
does not help (I run out of memory before I get sensible answers).

It is obvious what has to be done: an atom centered mesh (as appears in
DMol, for example) has to be used instead. However, before implementing
this (which is a *major* revision to the code), I would welcome any advice
>from those who have used such meshes. In particular:

o Are there any special considerations that have to be taken into account
  since I am working with solids?

o What are the best partition functions to use?

o What are the best quadrature schemes for the radial and for the angular
  integrals?

o How efficiently can such meshes be used for solving Poisson's equation
  in *solids*?

Cheers,

Andrew

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