[molpro-user] CI singles from SCF reference - spin symmetry issue

[Tatiana Korona]

On Fri, 28 Dec 2007, Dan Haxton wrote:

> Hello,
>
> I am trying to perform a very simple calculation
> on NO_2^+ with version 2002.6 in which I include all
> single excitations from a (closed-shell) SCF
> reference configuration.  I would like to do this
> for all spin and spatial symmetries, not only those
> of the SCF reference configuration.  Here is my
> input, done in cs symmetry with two irreps.
>
>
>
>
> geomtyp=xyz
>
> geometry
> 3
> myno2
> n    0.0        0.0     0.0
> o    0.0     1.12  0.01
> o    0.0     1.14  0.01
> end

1) Don't you get a message:

CAUTION
  VERY SHORT BOND LENGTHS PRESENT - IS THIS RIGHT?

Your oxygen atoms almost overlap. I wonder how your RHF converged at all. 
I tried with both 2006.3 and 2002.6 and my input died with
?TOTAL ENERGY UNREASONABLE

2) If you want to calculate CIS from closed-shell ref., then you can do 
this in 2006.1 for singlets and triplets (together with 1st order 
properties), see h2o_cis.test, and for singlets with 2002.6, see 
loc_eom3.test for input examples.

Best wishes,

Tatiana Korona

Dr. Tatiana Korona http://tiger.chem.uw.edu.pl/staff/tania/index.html
Quantum Chemistry Laboratory
University of Warsaw
Pasteura 1, PL-02-093 Warsaw, POLAND


`The man who makes no mistakes does not usually make anything.'
                                        Edward John Phelps (1822-1900)