Subject: BIG AB INITIO JOBS

From: "E. Lewars" <[email-masked]>
Date: Mon, 19 Feb 1996 12:17:12 -0500 (EST)

1996 Feb 19

Albeiro Restrepo asked about the biggest systems that have been studied by
ab initio, and the reliability of the results. I don't claim that these are the
biggest anyone has looked at, but they are at the high end of ab initio jobs:

(1) MP2(FC)/6-311G** (312 basis funtions) on  C6H5-C:::C-C6H5: S. Saebo and
    J. Almlof et al, THEOCHEM 59, 361 (1989).
(2) MP2/6-31G* optimizations on porphyrins, ca 20 heavy atoms. At the MP2 level,
    unlike the HF, the known, dampened bond alternation characteristic of these
    aromatic systems is evident. _Long_ calc's. See L. Paquette et al, ca. 1995
    (J Am Chem Soc?).
(3) For a short, very useful review of work on ab initio etc calc's and their
    reliability, see I. N. Levine, _Quantum Chemistry_, 4th Ed., Prentice Hall,
    1991, Chapters 15, 16, 17.

  Errol Lewars

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From: "Dr. James Brown" <[email-masked]>
Date: Mon, 19 Feb 1996 22:51:14 -0500

On Feb 19, 12:17pm, E. Lewars wrote:
> Subject: CCL:BIG AB INITIO JOBS

>     J. Almlof et al, THEOCHEM 59, 361 (1989).

A study of glucose by us in JACS coming out soon had 348 basis functions.
 Another on glucose conformers by Truhlar and coworkers to be published in
Carbohydrate Research included 624 basis functions.  As far as
reliability...it's difficult to tell since there's not much data on glucose in
the gas phase.

James