From chemistry-request@server.ccl.net Mon Mar 13 10:57:27 2000 Received: from kasei.materials.ox.ac.uk (kasei.materials.ox.ac.uk [163.1.64.46]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id KAA13848 for ; Mon, 13 Mar 2000 10:57:27 -0500 Received: from localhost (hfield@localhost) by kasei.materials.ox.ac.uk (8.9.3/8.9.3) with ESMTP id PAA15974 for ; Mon, 13 Mar 2000 15:59:38 GMT X-Authentication-Warning: kasei.materials.ox.ac.uk: hfield owned process doing -bs Date: Mon, 13 Mar 2000 15:59:38 +0000 (GMT) From: Andrew Horsfield X-Sender: hfield@kasei.materials.ox.ac.uk Reply-To: Andrew Horsfield To: Computational Chemistry List Subject: Gradient Corrections Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII 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 +----------------------------------------------------+ Andrew Horsfield e-mail: horsfield@fecit.co.uk FECIT, 2 Longwalk Road, Stockley Park, Uxbridge, Middlesex UB11 1AB, United Kingdom. phone: +44-(0)181-606-4653 FAX: +44-(0)181-606-4422 +----------------------------------------------------+