Subject: DIIS SCF in UHF and UDFT

From: Ed Brothers <[email-masked]>
Date: Wed, 15 May 2002 11:20:59 -0400

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
[email-masked]

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From: Mikael Johansson <[email-masked]>
Date: Wed, 15 May 2002 20:08:30 +0300 (EET DST)

Hello All!

What's the "proper" B3LYP reference to use? Usually Becke's paper [1] is
cited, and sometimes additionally the paper by Stephens et al. [2].

Paper [1] does not contain the B3LYP-functional, altough it defines the 3
parameters for the different types of contribution. Paper [2] explicitly
explains the alterations to Becke's original formulation, but I find
at least one earlier paper [3] mentioning/using B3LYP.

> From the articles, I assume B3LYP was something introduced by the Gaussian
program package, am I right? Furthermore, does anyone know of an even
earlier B3LYP reference than [3]?

[1] A.D. Becke, J.Chem.Phys. 98 (1993) 5648-5652
[2] P.J. Stephens, F.J. Devlin, C.F. Chabalowski, M.J Frisch,
    J.Phys.Chem. 98 (1994) 11623-11627
[3] K. Kim, K.D. Jordan, J.Phys.Chem. 98 (1994) 10089-10094

Have a nice day,
    Mikael Johansson
    University of Helsinki
    Department of Chemistry
    [email-masked]
    http://www.helsinki.fi/~mpjohans/
    Phone: +358-9-191 50185
    FAX  : +358-9-191 50169

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From: Roy Jensen <[email-masked]>
Date: Wed, 15 May 2002 10:53:38 -0700 (PDT)

Is it possible to do a multireference CI calculation using Gaussian 98? If
so, could someone provide a typical input file.

Roy Jensen

I will summarize to the List.