Subject: [Q] G94 Excited States

From: Ernst Wallenborn <[email-masked]>
Date: Mon, 20 May 1996 10:25:33 +0200

Hi there,

i need to calculate an electronic spectrum of an aromatic compound  
(yes it was my boss' idea, yes i did tell him that this is much
easier to measure and no fun to calculate, no he didn't
find my opinion useful and constructive).

Now the problem is: the thing is far too big for US-GAMESS
(USG has no direct CI, hence it's not expensive to calculate,
it's plain impossible with our HD configuration), it is
too big for a reasonable CAS in g94 (i have a Pi space
of 20 orbitals, of which at least ten have to be included)
CIS on the other hand takes (STO-3g, this was a test)
about 30 minutes on my SPARC 2, but it's results
are, well, not overwhelming.

So the question is: Is there any possibility of doing anything
better than CIS but cheaper than CAS in g94? In GAMESS i'd
do a CISD versus CISD(T) calculation in the style of Shavitt's
70's calculation of the acetone spectrum, but as i mentioned, i think
US-GAMESS is likely to fail. 

I tried 
#3-21g* casscf(10,10,nroot=1) iop(4/17=10,4/18=10,4/19=1)
where the 4/19 option should have set up a FOCI MCSCF (in
GAMESS language), but ended up with a eof error on stdin.
After checking the programmer's manual i added 
   64    1    1
    1    2    3    4    5    1    2    3    4    5    
to the .com, where 64 is the number of occupied orbitals,
and 1 2 3 4 5 1 2 3 4 5 the reference configuration.
That gave me lots of TAPE READ ERRORs.

Besides a test run on water showed a difference between
4/19=2 and GAMESS MCSCF SOCI=.T., so they are not identical 
anyway.

Any help?

-- 
-ernst wallenborn.

i'm not a bug.
i'm an undocumented feature.