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

[Peter Knowles]

If you want to see comparable CI wavefunctions for the ground state in both cases, you probably want to explicitly obtain the natural orbitals for the ground state, rather than the eigenvectors of the average density matrix. See http://www.molpro.net/info/current/doc/manual/node239.html

Peter

On 17 Mar 2011, at 06:32, 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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--
Prof. Peter J. Knowles             
School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK
Email KnowlesPJ at Cardiff.ac.uk 
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