Subject: summary_errors in comp chem.

From: Bernd Engels <[email-masked]>
Date: Fri, 11 Jun 1999 10:29:40 +0200 (MES)

Below please find a summary of the responses
I got to the following question:

>I am looking for systems which are theoretically
>difficult. I am interested in all kind of systems,
>i.e. in systems which makes problems for DFT and/or
>Coupled Clusters and/or Moller-Plesset etc.
>there should be a lot of systems which are
>really problematic and (what a pity) where the
>problems where never published. 

Thanks a lot to all who have answered.
It was really interesting.
Bernd Engels

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Dear Prof. Engels,

	I have started to put together a web accessible database of molecules and
particular theoretical methods which produce poor results. It doesn't have
many species in it yet. I have it running on a small web server which is
currently at:

http://h194161.nist.gov/sicklist/sicklist.html

I hope to move it to a better server in the next month or so at which point
he address will change. It is set up so that anyone can make a
contribution. If the number of entries gets large enough I can add methods
for searching by molecule or method or whatever.

	It may have some suggestions of the sort you are looking for. I was hoping
to catch problems that don't get published. I would welcome any comments
you have about the Sicklist database. Please do not give out the address.
When I get it moved to the better web server I will make a posting on the CCL.

Russ Johnson

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

The base properties of N2O are a problem.
See J. E. Del Bene, E. Stahlberg, and I. Shavitt
Int. J. Quantum Chem. Quantum Chem. Symp. 24, 455 (1990).
This paper has references to some earlier work as well.
Regards,
Janet Del Bene

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 hi Bernd,
    You can try to calculate FeO - both ground and excited state. good luck!
                                                 Pradipta 
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Bernd,

the trichlorine radical, Cl3, seems to be quite difficult; see Kaledin et
al., J. Chem. Phys. 108, 2771 (1997).

Best regards,

Ole Swang

Status: RO
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Dear Bernd,

At the last ACS meeting, Karl Irikura reported that his group at NIST is
developing several resources to be made readily available in support of QC
applications:

 http://www.nist.gov/compchem

One of these developments is to collect examples of known failures of
specific methods into a "Quantum Chemistry Sicklist Database."  This sounds
very much like what you are looking for:

>I am looking for systems which are theoretically
>difficult. I am interested in all kind of systems,
>i.e. in systems which makes problems for DFT and/or
>Coupled Clusters and/or Moller-Plesset etc.
>there should be a lot of systems which are
>really problematic and (what a pity) where the
>problems where never published.

I think part of their interest is just what you described: that it is a
pity they were never published so researchers can avoid pitfalls and
theoreticians can focus on where methods need improvement.  You should get
in touch with Karl's group at NIST, and see what they have collected so far.

EC
---

Ernest Chamot
Chamot Laboratories, Inc.
530 E. Hillside Rd.
Naperville, IL 60540
(630) 637-1559
[email-masked]
http://www.chamotlabs.com/cl

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Bernd,

	Here are a few suggestions.

Transition metals, particularly open shell and multiple bonded ones.
Au which is sensitive to relativistic effects.
F2 and FOOF which are correlation sensitive.
Jahn-Teller distortions which are correlation sensitive.

	Please post a summary to the CCL.

                                Dave Young
                                [email-masked]