Subject: Gradient Corrections

From: Andrew Horsfield <[email-masked]>
Date: Mon, 13 Mar 2000 15:59:38 +0000 (GMT)

Hi,

I am thinking about adding gradient corrections to a density functional
code that works with numerical atomic type orbitals. Given that there are
a number of functionals in the literature, I would welcome suggestions of
where to start. Note that I cannot include any exact exchange since it is
too expensive to evaluate the integrals with numerical orbitals.

In particular, questions that come to mind are:

1) Is exchange better described by gradient corrections than correlation
   (i.e. would implementing just Becke exchange be a worthwhile move)?

2) Is the correct choice of functional very problem dependent? Is there
   one choice that gives better *overall* results than the others?

3) Are there other methodologies for improving on LDA besides gradient
   corrections? If so, what (dis)advantages do they have?

Cheers,

Andrew

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