Subject: Summary:Pseudopotential+AIM

From: "Miguel A. Ramírez" <[email-masked]>
Date: Tue, 19 Mar 2002 11:59:38 -0000

Dear CCLers,

Some times ago, I posted this question:

Please, I'm working with structures containing Co-Co bonds. I'm using LANL2DZ as pseudopotential for the core electrons of the cobalt, In thats conditions, could I use AIM methodology to analyse the molecule?. Thank you

Thanks for the useful replies:

======================================================================

Hi Miguel,

I think you could, but... As far as I know AIM needs the total electron
density to be able to produce sensible results. So if you are using a
pseudopotential you will need to add the density of the core electrons
back in before you feed your density to the AIM package.

Huub

--

========================================================================

Huub van Dam                               E-mail: [email-masked]
CCLRC Daresbury Laboratory                  phone: +44-1925-603362
Daresbury, Warrington                         fax: +44-1925-603634
Cheshire, UK
WA4 4AD

========================================================================
Hola Miguel,

Lo que ocurre cuando se usan pseudopotenciales, es que el máximo (punto
crítico 3,-3) en el núcleo se transforma en un mínimo (3,+3), y eso puede
hacer que el PC de enlace (3,-1) no aparezca, y que aparezcan máximos (3,-3)
en la capa de valencia del metal. En todo caso, todo depende de la molécula,
y en concreto del tipo de enlace entre los átomos que usan
pseudopotenciales, así que lo mejor es realizar pruebas. Te recomendaría el
artículo  Journal of Computational Chemistry, Vol. 18, No. 3, 416-429 (te lo
puedo enviar por correo, si no tienes acceso a él).

Yo he hecho bastantes cálculos con LANL2DZ (aunque ninguno con enlace
metal-metal) y en general los PC de enlace los localizo sin problemas, y
además presentan valores de densidad, laplaciana,... correctos. Eso sí, al
no existir máximo en el núcleo, el "bond path" no conecta el PC de enlace
con el PC (3,-3) en el núcleo. También puedo realizar las integrales sobre
los átomos sin problemas.
Un grupo que ha trabajado con LANL2DZ y enlace metal-metal es el del difunto
J. M. Molina, de Granada. Te puedo recomendar esta referencia Journal of
Molecular Structure (Theochem) 493 (1999) 249-257, pero estoy seguro que
tienen más artículos sobre el tema.

Espero que la anterior te sirva de ayuda. SI tienes alguna duda, no dudes en
preguntarme, aunque yo no soy ni mucho menos un experto en el tema.

Un saludo

Pablo

--------------------------------------------------------
Pablo Vitoria Garcia
Dpto. Química Inorgánica, Facultad de Ciencias
Universidad del País Vasco (UPV/EHU)
Aptdo. 644
48080 Bilbao (Bizkaia)

Tfno. 94 6012579
Fax. 94 4648500
______________________________________
I am not sure in your specific case but I do know that pseudo potentials can give incorrect numbers of critical points in the electron density (i.e. 1 Bond Critical Point) in a water molecule compared to the usual two. As such I would also expect other features of the density to be different too. Personally I would not trust pseudopotential calculations. 
regards, 

Sean O'Brien 
*********************************************************************************
Dr. Sean E. O'Brien
Cancer Research Laboratories
School Of Pharmaceutical Sciences
University of Nottingham
University Park
Nottingham
NG7 2RD
0115 951 3423
*********************************************************************************  
  miguel,

it is possible to use AIM with pseudo potentials, there is a paper by 
ron gillespie and richard bader among others from a few years back that
examined the changes in topolgy seen when usin such bases, and the
effect of the size of the valence functions, i think that the conclusion
was that you should NOT use a minimal basis for TM compounds.

noj
-- 
  Dr. N.O.J. Malcolm                       [email-masked]
  Chemistry Department                   
  UMIST, Sackville Street
  Manchester, England. M60 1QD

____________________________________________________________

Hola,

Yes, you can use AIM to analyze your electronic density. The difference
between a pseudopotential calculation and a full electron treatment is the
core density, which does not exists when using pseudos. But that not
affects the form of the valence density, which is what you want to analyze.

Hope it helps
 ________________________________________________________________

  Carles Bo
  Dept. de Quimica Fisica i Inorganica
  Universitat Rovira i Virgili          Voice +34 977 55 9569
  Pl. Imperial Tarraco, 1              FAX   +34 977 55 9563
  43005 - Tarragona                 
  SPAIN                         http://www.quimica.urv.es/~w3qfi
                   http://www.quimica.urv.es/cgi-bin/card?bo+qfi
________________________________________________________________

You'll have to drill back through articles around 1994 from Gernot
Frenking, but the basic answer is, "Not Really".  Because of the missing
core electrons, there are problems determining the bond paths near the
atoms using the ecps.

You could also check my paper in Organometallics, 1999, 18, p4800 on
Ruthenium Silylenes, where I compared the bond critical point values and
energy densities determined by AIM with the LANL2DZ ECP on Ruthenium.
The critical point values are low when compared with the all electron
case.

Frenking's article (which I can't find this morning quickly) discusses ECP
vs. All Electron, plus a couple of schemes to try to replace the core
density.  None are consistently successful.  You should also look in
Inorganic Chemistry around 1994/1995 when Gillespy and Bytheway discuss
polarization of formally core electrons by strong ligands in early TM
oxo-fluorides, and effect that would be lost if ECPs were used.

-Fred

Frederick P. Arnold, Jr.
NUIT, Northwestern U.
[email-masked]

__________________________________________________________
In principle you can but you have to add back in the "missing" electrons
before proceeding with the analysis.
 
--David Shobe
Süd-Chemie Inc.
phone (502) 634-7409
fax     (502) 634-7724
email  [email-masked]

__________________________________________________________________

In fact, it's impossible to use pseudopotential with AIM.
I suggest  you to make a simple point energy calculation at a higher level with a full basis set like DZVP
You can find it and other basis sets at the address
http://www.emsl.pnl.gov:2080/forms/basisform.html

Sincerely yours

Etienne Derat
-- 

Etienne Derat
Doctorant
Groupe Modélisation et Réactivité Chimique 
UMR 6519 "Réactions sélectives et Applications"
Université de Reims Champagne-Ardenne

Tél : +33 3 26 91 32 45
Fax : +33 3 26 91 31 66
________________________________________________
Dr. Mu=F1oz,

   The problem with using AIM and molecules using described with ECP's
is that the integration of the density requires the full density.
I know of no implementation of AIM that can either work without that
core density or can "replace" it by analyzing the core potential.

   So in short, no there is no option for using AIM with ECP's.

Douglas J. Fox
  Technical Support
  Gaussian, Inc.
  [email-masked]
_________________________________________________
=============================================

Dr. Miguel A. Ramírez Muñoz
Instituto Universitario de Bio-Orgánica "Antonio González"
Universidad de La Laguna
Astrofísico Francisco Sánchez, nº 2
38206, La Laguna, Tenerife, Spain
     Tfno: (22)318594
      [email-masked]
      http://webpages.ull.es/users/mramirez.htm