Subject: Re: CCL:Broken symmetry calculations

From: David Case <[email-masked]>
Date: Mon, 26 Nov 2001 08:44:57 -0800

On Mon, Sep 17, 2001, temper wrote:
> 
> In the course of the theoretical ab initio treatment of magnetic exchange
> in dinuclear transition metal systems some authors use the method of broken 
> symmetry. Is there anybody to help me in how to do broken symmetry calculations?
> Is there any recipe for it?

On of the more detailed early discussions of this is in the following
review:

%A L. Noodleman
%A D.A. Case
%T Density-functional theory of spin polarization and spin coupling in
iron-sulfur clusters
%J Adv. Inorg. Chem.
%V 38
%P 423-470

As for "how-to": this is discussed in many papers.  Generally, we recommend
converging first a high-spin (fully symmetric) SCF calculation, then
exchanging the alpha and beta spins on one side of the molecule to create
a starting configuration for the broken symmetry calculation.  Exactly
how to "flip spins" depends on the program you are using.  ADF and Jaguar
(maybe others) offer built-in support for this; with other programs one
generally has to manually edit a molecular orbital coefficient file or
something similar to that.  Be prepared for convergence difficulties (that
is, be prepared to be patient).

...hope this helps...dac

-- 

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David A. Case                     |  e-mail:      [email-masked]
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