----- Original Message -----
Sent: Friday, June 08, 2007 12:35
Subject: CCL:G: post-Hartree
claculations, advice needed
I hope that somebody could give me some advice.
I want to calculate energies for dimers and trimers to extract accurate
potentials using post Hartree methods (also for "large" distances > 5
Angstroms). I intend to do this for closed- and open-shell systems (UHF)
consisting of simple atoms (in the moment).
Because I am not a computational chemistry specialist I did some reading
and as a result I concluded that methods like MP4, CCSD and QCISD might be
appropriate using a basis set like aug-cc-pVQZ might be appropriate.
I did success-full calculations for Ar dimers with gaussian g03
reproducing published results which made me confident. I failed for trimers
using these evolved methods so long, however (might be due to that I have only
a 32 bit compiled version and the required real memory exceeds 2.2 GB possible
with 32 bit, I do have 8 GB, however). MP2 trimers with more simple basis sets
work, but that might be not what I want?
Now my questions are:
1. are the methods described above adequate?
2. which of the many programs available could be recommended to
Prof. Dr. Matthias Gottschalk
tel/fax +49 (0) 331 288-1418/1402