No binding of Pt2!

[Joris Kuipers]

Hello everyone,

I hope someone can help me or if someone has experienced this problem too.

No matter what kind of method you use (CCSD, Multi with CC, MRCI, MRPT2, etc.) no 
more than 1 milihartree of binding is found for Pt2 opposed to the GAMESS program 
package which gives a binding of ~ 2 eV.

I compared the way molpro describes the orbitals and what kind of references 
(configurations) should be taken into account. I'm using the ECP60MHF effective core 
potential (to deal with the large Pt) and using the corresponding s, p and d basis.

I'm suspecting that these core potentials are not fully functional for larger elements so 
that they do not deal properly with the relativistic effects.

Does anyone recknognize this problem or does anybody know what else could be 
causing this discrepancy? As many of you know Pt2 has more binding than the 
vanderwaals forces! I hope someone can give me some feedback.

Taken from my input:

 geometry={angstrom;
           Pt1
           Pt2,1,R1(k)}


 gprint,basis,orbital,cs,cp
 basis = {
 ecp, Pt,ECP60MHF
 spd,Pt,ECP60MHF;
 }


Kind regards,

Joris Kuipers


Leiden Institute of Chemistry, Gorlaeus Laboratories.
Leiden University;Einsteinweg 55 / P.O. Box 9502 2300RA, Leiden The Netherlands.
Phone:        +31 71 5274400    TeleFax:      +31 71 5274537
Department:                     Phone:        +31 71 527