Subject: SAM1 semiempirical method

From: Andy Holder <[email-masked]>
Date: Tue, 29 Feb 2000 09:16:20 -0600

Colleagues,

Several days ago the following questions were posed.  Sorry it took me some
time to respond.

> In 1993 the Dewar group announced the development of the SAM1 ("semi ab
> initio #1") method.
> I know the basic principles behind it, but would like to know:
> 1) What became of it? It does not seem to appear much in the literature.

The SAM1 method is still under development in my Group at the University of
Missouri-Kansas City.  We are working on refining some additional parameters
and have added some new computational algorithms (an improved CI (1) and a
quadratically (to be published) convergent SCF procedure) to make the method
tractable for open-shell transition metals.  The references to the method
currently extant in the literature are listed below.  A major paper
describing the full implementation and listing parameter values is in
preparation.

> 2) Did computational chemists conclude it is not  much better than AM1,
> and so let it fall into   disuse?

Actually, SAM1 performs better than AM1 in most cases for CHON and the
halogens.  We have parameters for Si, S, P that are better than AM1 as well,
especially for hypervalent species.  The TM parameters for Fe, Cu, and Zn
are basically completed and others are underway.

> 3) I think it is offered in AMPAC; does any other  package have it?

Currently Semichem's AMPAC is the only program in which it has been
implemented, but we expect other vendors to put it in when the theoretical
paper and parameters are published.

References:
-----------
(1) [CI paper] Liotard, D.L.;  Holder, A.J.  J. Chem. Inf. Comput. Sci.
    1999, 39, 587.
(2) [SAM1] Dewar, M. J. S.; Jie, C.; Yu, G. Tetrahedron 1993, 23, 5003.
(3) [SAM1] Holder, A. J.; Dennington, R. D.; Jie, C. Tetrahedron 1994,
    50, 627.
(4) [SAM1] Holder, A. J.; Evleth, E. M. in Modeling the Hydrogen Bond;
    Smith,  D. A.;  American Chemical Society, Washington, DC, 1994;
    p 113.

Regards, Andy Holder

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UUUU  UUU MMM   MMKK KKKK   CCCC   |           ANDREW J. HOLDER
 UU    U   MM   MMK   K    CC  CC  | Assoc. Prof. of Comp./Org. Chemistry
 UU    U   MMM M MK KK    CCC      |          Dept. of Chemistry
 UU    U   M MM  MK   KK   CC  CC  |  University of Missouri-Kansas City
  UUUUU   MMM M MMKK   KK   CCCC   |         Kansas City, MO  64110
                        KK         |            [email-masked]
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