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

[Hans-Joachim Werner]

This is because in a two-state calculation the state-averaged density
matrix is used by default to compute the final natural orbitals. It is also possible
to use a state-specific density, see NATORB directive in the manual.
Of course, the ci-coefficients depend on the orbitals.

Best regards
Joachim Werner 
Am 17.03.2011 um 07:32 schrieb Terry Frankcombe:

> 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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