[molpro-user] Error in CI calculation.

[Peter Knowles]

It seems to me that the high-spin open-shell determinant that you  
converge on with the MCSCF program is not the lowest in energy in its  
symmetry; I would expect to see single occupancy in orbitals of  
symmetries 2 and 4, perhaps
occ,15,5,13,5;closed,11,4,9,4;
You can test this out by running CASSCF calculations with slightly  
enlarged active spaces.

Peter Knowles

On 7 Sep 2006, at 08:46, Wang Mingwei wrote:

> Hello everyone,
>
> I have met following same error several times when I do a CI  
> calculation for the state of the highest spin multiplicities for  
> different molecules:
>
>  Number of core orbitals:          28 (   9   5   9   5 )
>  Number of active  orbitals:       10 (   5   0   5   0 )
>  Number of external orbitals:     338 ( 114  72  97  55 )
>
>  Molecular orbitals read from record     2140.2  Type=MCSCF/NATURAL  
> (state 1.3)
>
>  Coulomb and exchange operators available. No transformation done.
>
>  Number of p-space configurations:   1
>
>  Reference wavefunction optimized for reference space (refopt=1)
>
>  State     Reference Energy
>    1       -2462.39035181
> ..................
> ...............
>   ITER. STATE  ROOT      NORM       CORR.ENERGY   TOTAL ENERGY    
> ENERGY CHANGE       DEN1      VAR(S)    VAR(P)      TIME
>     1     1     1     1.00000000     0.00000000 -2462.39035181      
> 0.00000000    -0.10178291   0.00D+00  0.19D+00     1.32
>     2     1     1     1.31183661    -0.12878874 -2462.51914055     
> -0.12878874    -0.02840665  0.24D-02  0.20D+00    35.64
>
>  NO VECTOR OF INTERNAL CI OVERLAPS SUFFICIENTLY WITH REFERENCE  
> VECTOR 1. INCREASE NSTATI!
>
>  OVERLAP BETWEEN INITIAL AND PRESENT VECTORS
>                    1
>          1     0.0602475
>  ovmax=   6.02475161923600D-002   ovref=   6.02475161923600D-002
>
>  ERROR EXIT
>  CURRENT STACK:      CIPRO  MAIN
> And the following is the corresponding input file:
>  ***,MnOMnO
>  memory,250,m
>  gprint,orbital,basis
>  geomtyp=xyz
>  geometry={
>  x,y
>  4
>  This is geometry input for MnOMnO with an xyz file
>  Mn  0.000000    -1.791410   -0.037003
>  O   1.369376    0.000000    0.115635
>  O  -1.369376    0.000000    0.115635
>  Mn  0.000000    1.791410   -0.037003}
>
>  basis={spdf,Mn,Bauschlicher-ANO;
>         spd,O,6-311G*}
>
>  dkroll=1
>
>  rhf
>  closed,12,5,11,5;
>  wf,66,1,0
>  orbprint,5
>
>  multi
>  occ,14,5,14,5;
>  core,9,5,9,5;
>  wf,66,3,10;
>  maxiter,50
>
>  mrci
>  occ,14,5,14,5;
>  core,9,5,9,5;
>  wf,66,3,10;
>  option,maxiti=500
>
>  mrci
>  occ,14,5,14,5;
>  core,9,5,9,5;
>  wf,66,1,0;
>  option,maxiti=500
>
> My question is why such error occurs and how I could avoid such   
> error.
> Thanks.
> mingwei
>

--
Prof. Peter J. Knowles
School of Chemistry, Cardiff University, Main Building, Park Place,  
Cardiff CF10 3AT, UK
Telephone: +44 29208 79182 Fax: +44 2920874030
Email KnowlesPJ at Cardiff.ac.uk  WWW http://www.cardiff.ac.uk/chemy/ 
staff/knowles.html