Subject: 2E" state

From: HAJGATO Balazs <hajgato:at:qpcrkk.chem.tohoku.ac.jp>
Date: Fri, 03 Oct 2003 12:57:57 +0900

Dear CCL-ers,

I am trying to calculate the single electron affinity of a molecule in 
the D3h pont group. The homo of the neutral molacule is E' and the lumo 
is E". I have calculated the neutral one and the orbital energies are 
perfect in almost all the cases. But I have problems with the single 
negative ion. I should be in 2E" state. So I have to use some multi 
reference method because single reference methods (MP2, CCSD and so on) 
give broken symmetry. So I tried CAS. I was able to calculate the 
neutral and the single negative ion and I have perfectly degenerated 
occupancies. (I used molcas, in Cs symmetry averaged ground and first 
excited state). But my problem is that I also need some dynamic 
correlation. I tried to calculate MR-SDCI with molcas (using 
supersymmetry) with RASSCF and MRCI modules, but I get always wrong 
occupancies (no degeneracy in energies/occupancies). I also tried to use 
  molpro (version 2000.1) but in case of cas I get wrong occupancies. 
Using MR-SDCI for the negative ion with the necessary additional 
reference symmetries I still get wrong occupancies. I also tried ACES2 
mr-bw-ccsd method with averaged ground and first excited states but I 
dont know to much about the mr-bwccsd method and with using diffuse 
basis set the CCSD dont converge. (and sometimes simply dumps core the 
program). My question is what kind of onther programs /methods are 
available to calculate the 2E" state? Is mr-bwccsd is capable to 
calculate doublet states as well? I see only singlet,triplet, and 
quintet mr-bwccsd calculations. Any suggestions are welcome.

Regards,

B. Hajgato