[molpro-user] Re: FCI calculation

[rama chandran]

Thank you for the previous two replies  
I incorporated both and the job it works



--- Peter Knowles <KnowlesPJ at Cardiff.ac.uk> wrote:

> The occ directive in FCI defines the numbers of
> orbitals in each  
> symmetry that are included in the FCI calculations.
> In your inputs you  
> have specified this as just the valence orbitals.
> With CASSCF orbitals  
> you should then get just the CASSCF energy, and with
> other orbitals,  
> something higher. If you want the full calculation
> including the  
> complete basis, simply omit occ.
> Peter
> On 29 Jan 2008, at 11:40, rama chandran wrote:
> 
> > Dear Molpro users,
> > I did one molpro calculation for a triatomic
> linear
> > system containing 3 electron  HeH2+ linear.
> > Earlier the energy for this system was reported to
> be
> >
> >
> >        MRCI            CASSCF          HF-SCF
> >     -3.51818587     -3.48901389     -3.47036561
> >
> > using th input
> >
> >
> > ***,HeH2plus
> >  Memory,100,M
> >  geometry={H;
> >  H1,H,r1;
> >  He,H,r2,H1,a1}
> >   r1=2.075338
> >   r2=1.931059
> >   a1= 180.0
> >  basis=v5Z
> > {HF
> > occ,2,0,0,0
> > wf,charge=1,symmetry=1,spin=1
> > }
> > casscf
> > mrci
> >
> >
> > I tried to redo the problem using  Full-CI
> > calculations
> > I tried it in 3 different ways as I have not done
> any
> > full CI calculations before...
> > when I tried with the keyword fci alone without
> > specifying anything else it terminated with the
> error
> > saying that orbital record not found.
> > Then I specified the wavefunction details as
> above,
> > still the same error.
> > Then I did the fci followed taking  previous hf
> > wavefunction   and also another calculation in
> which
> > fci taking casscf wavefunction as follows,
> >
> > ***,HeH2+intermediate-example-FCI
> > memory,50,m
> > geometry={H;
> >  H1,H,r1;
> >  He,H,r2,H1,a1}
> >   r1=2.075338
> >   r2=1.931059
> >   a1= 180.0
> > basis,H=v5z
> > !define basis
> > hf
> > {fci
> > occ,2,0,0,0
> > wf,charge=1,symmetry=1,spin=1
> > }
> >
> >
> >
> > and
> >
> >
> > ***,HeH2+intermediate-example-FCI
> > memory,50,m
> > geometry={H;
> >  H1,H,r1;
> >  He,H,r2,H1,a1}
> >   r1=2.075338
> >   r2=1.931059
> >   a1= 180.0
> > basis,H=v5z
> >
> > {casscf
> > occ,2,0,0,0
> > wf,charge=1,symmetry=1,spin=1
> > }
> > {fci
> > }
> >
> > both gives the same energy as -3.50605528 Hartrees
> >
> > As you see this energy is very much different from
> the
> > values they reported through MRCI calculations....
> > I was expecting a lower energy through full CI
> > calculations.  Is something wrong....??
> >
> > Can anyone advice me with some details?
> >
> >
> >      Download prohibited? No problem. CHAT from
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> 
> --
> 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/contactsandpeople/academicstaff/knowles.html
> 
> 
> 



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