Subject: Excited States by GAMESS

From: Budong Peng <[email-masked]>
Date: Fri, 3 Dec 1993 17:25:20 -0500

Dear netters;

    Currently I am working on the Formamide and Formamide-H2O complex
with the GAMESS software.

For Formamide HCONH2,
I can reach the electronically excited states by UHF run with MULT=3.
With the output from this I did a MCSCF OPTIMIZ(E)ation and get the total energy
to be higher than the ground state (in MCSCF as well). The $DRT group for
SCFTYP=MCSCF is
 GROUP=C1
 FORS=.TRUE.
 IEXCIT=2  (I found that it doesn't matter how much is IEXCIT)
 NDOC=11
 NVAL=0
 NALP=2

When I tried to get to the excited singlet state,
I replaced NALP=2 by NAOS=1 NBOS=1
However, the final energy is slightly LOWER than the ground state!
Since I specified two singly occupied molecular orbitals, should this be
an excited state?

I am very puzzled by this. Another question I have is that how do I get
to higher excited states with electron at a high orbital but leave lower
orbitals empty? I couldn't figure out by reading the reference.

For Formamide-H2O complex,
I can't even specify MULT=3 and do a UHF calculation, the program will
stop at the first NSERCH and say too many iterations before it can
converge. Is it because that the complex has two molecules and the
program is confused about how to get at the excited state? Is it quite
different for one and two molecules?

I would appreciate any advice and suggestionn. Thank you very much.

Budong Peng