From chemistry-request -A_T- server.ccl.net Wed May 15 11:20:59 2002
Received: from f04n07.cac.psu.edu ([128.118.141.35])
	by server.ccl.net (8.11.6/8.11.0) with ESMTP id g4FFKxs14612
	for <chemistry#* at *#ccl.net>; Wed, 15 May 2002 11:20:59 -0400
Received: from psu.edu (amoeba.chem.psu.edu [128.118.172.90])
	by f04n07.cac.psu.edu (8.9.3/8.9.3) with ESMTP id LAA391178
	for <chemistry- at -ccl.net>; Wed, 15 May 2002 11:20:59 -0400
Message-ID: <3CE27CDC.12A26EC0;at;psu.edu>
Date: Wed, 15 May 2002 11:20:59 -0400
From: Ed Brothers <enb108 _-at-_)psu.edu>
Reply-To: enb108 {*at*} psu.edu
Organization: PSU Merz Group
X-Mailer: Mozilla 4.61 (Macintosh; I; PPC)
X-Accept-Language: en,pdf
MIME-Version: 1.0
To: chemistry _-at-_)ccl.net
Subject: DIIS SCF in UHF and UDFT
Content-Type: text/plain; charset=us-ascii; x-mac-type="54455854"; x-mac-creator="4D4F5353"
Content-Transfer-Encoding: 7bit

    I am currently implementing DIIS to accelerate SCF convergence as
per Pulay, J. Comp. Chem., V 3, #4, 556-60, 1982.  In the RHF
case the construction of the error vectors is fairly straight forward:

    e(i) = F(i) D(i) S - S D(i) F(i)

Where i is the step index, F is the operator matrix, D is the total
density matrix, and S is the overlap matrix.   I am a bit unsure how to
proceed
with the unrestricted case.  I have implemented


     e(i) = Fa(i) Da(i) S - S Da(i) Fa(i)  + Fb(i) Db(i) S - S Db(i)
Fb(i)

Where the a and b are the alpha and beta electron versions of the
matrix.  This causes the generation of of a single B matrix and thus a
single set of coefficients from the linear equation.

Is this the right way to set up the error matrix for step i in UHF and
UDFT?  If it isn't, what is?  Dose anyone know a reference where this
is discussed?

Thanks for your time.
Ed Bothers.
Merz Goup, Penn State
enb108 -A_T- psu.edu