[molpro-user] CI vectors, single vs. multiple state calcs

[Toru Shiozaki]

Dear Terry,
I think this is because the CI vector is printed out after constructing natural or canonical orbitals (dependent on your input). The natural/canonical orbitals here are, in state,n (n>1) cases, made from the state-averaged density or Fock matrix; and therefore they are affected by the numbers of states.
Note that dont,orbital does disable the orbital rotation between occupied and external orbitals, but it does not mean that the original orbital is kept unchanged throughout.

If you use "locorb" directive (see an example below), whose orbital construction is not affected by state averaging, you will see completely identical coefficients.
Best wishes,
Toru

! sample example here ---
gprint,civectors,orbitals
gthresh,gradient=1.0d-10
charge=1
geometry={c;h,c,2}
hf
multi
{multi;locorb;dont,orbital}
{multi;locorb;state,2;dont,orbital}

On Mar 17, 2011, at 7:32 AM, Terry Frankcombe wrote:

> Hi folks
> 
> I'm doing what one might describe as CAS-CI in a (14,9) active space of
> a large system, using Multi.  The orbitals come from a previous CASSCF
> calculation.  I don't understand the results I get for doing a 2 state
> calculation.
> 
> The two commands (in two different jobs, all other aspects being
> identical) are:
> 
> {CASSCF; occ 67; closed 58; WF 130 1 2; dont orbital}
> {CASSCF; occ 67; closed 58; WF 130 1 2; state 2; dont orbital}
> 
> The jobs run fine.  The ground state energy is identical in each case
> (and identical to the energy from the CASSCF calculation that the
> orbitals come from, as expected).  However, for the CI vectors I get:
> 
> CI vector
> =========
> 
> 222222aa0      0.9713361
> 222220aa2     -0.2062039
> 
> for the single state calc and
> 
> CI vector
> =========
> 
> 222222aa0      0.8989227   0.2567884
> 22222a2a0     -0.2150793   0.6329933
> 2222220aa     -0.2237106   0.4707357
> 22222a0a2      0.0532983  -0.2444110
> 2222202aa      0.0534625  -0.2372961
> 222222a0a      0.0722705  -0.2227077
> 22222abaa     -0.1444124  -0.1890428
> 222220aa2     -0.1682664  -0.0702741
> 22222aa20      0.0920977  -0.1629586
> 22222baaa      0.0944303   0.1467891
> 22222aaab      0.0683397   0.1165439
> 22222aa02     -0.0352542   0.0965585
> 22222a02a      0.0491501   0.0911501
> 222220a2a     -0.0008757   0.0870140
> 22222aaba     -0.0183576  -0.0742902
> 22222a20a     -0.0611334  -0.0626342
> 2222a22a0      0.0012538   0.0506651
> 
> for the 2 state calc.
> 
> Why are the two CI vectors for the ground state so different?
> 
> As I understand things, the CI vector is essentially the eigenvector of
> a matrix which should be the same in both cases.  The energy calculated
> for the second state is well separated.  Can anyone help me understand
> what is going on here?
> 
> Regards
> Terry
> 
> 
> -- 
> Dr. Terry Frankcombe
> Research School of Chemistry, Australian National University
> Ph: (+61) 0417 163 509    Skype: terry.frankcombe
> 
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