Brueckner orbitals

[Dave Moore]

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Dear Dr. Werner,

Thank you very much for your reply.  I look forward to the new
version of MOLPRO.  As far as the Brueckner orbitals are concerned, I
am interested in using them to compute molecular properties as laid
out by Hesselmann and Jansen in CPL 315 p.248 [1999].  I am aware
that the treatment laid out therein is not strictly rigorous, however
the agreement with literature values seemed satisfactory.  Their
method seems to provide a cheaper way to calculate such quantities
than finite field calculations, and the densities so obtained provide
at least a qualitative measure of the correlation effects (relative
to SCF calculations).  Anyway, thank you very much for adding this
functionality to MOLPRO.  Sincerely,

Dave Moore
Chemistry Dept.
University of North Carolina at Chapel Hill

- -----Original Message-----
From: owner-molprouser at tcpc3.bham.ac.uk
[mailto:owner-molprouser at tcpc3.bham.ac.uk]On Behalf Of H.-J. Werner
Sent: Tuesday, September 25, 2001 12:11 PM
To: molpro-user
Subject: RE: Brueckner orbitals


This is to inform you that in the upcoming version 2001.1 the 
first-order density matrices will be available for MP2 and QCISD
and can be in dump records as usual. The same is true
for the corresponding natural orbitals. I am sorry, but 
this feature is not and will not be available in 2000.1.

Following your note, I will also modify the program to store
the Brueckner orbitals in a dump record. However, I do not
believe that it is a correct appraoch to use the Brueckner
orbitals to produce a density matrix. The correct effective
densities require to perform CPHF and CPCC calculations in order
to compute the response of the orbitals and amplitudes. This
is rather complicated stuff and unfortunately not so quick
to implement for all methods (CCSD, MP3 and MP4 are under way).

Best regards
H.-J. Werner

> Hash: SHA1
> 
> Hello,
> 
>       Thank you very much for your helpful reply.  I have made a
> little progress, but unfortunately I am still having trouble
> building the density matrix.  I think this is because the orbital
> occupations for the new record formed from the brueckner
> coefficients are unknown .. therefore no orbitals are used by the
> "DENS" command in MATROP no
> matter what I specify for "occupation".  Is there any way to
> determine or specify the occupations of the orbitals before I make
> the call to dens?  Thank you very much for your help.
> 
> Dave Moore
> 
> 
> - -----Original Message-----
> From: owner-molprouser at tcpc3.bham.ac.uk
> [mailto:owner-molprouser at tcpc3.bham.ac.uk]On Behalf Of Andreas
> Hesselmann
> Sent: Tuesday, September 25, 2001 8:33 AM
> To: molpro-user at tcpc3.bham.ac.uk
> Subject: Re: Brueckner orbitals
> 
> 
> Hello,
> 
> there unfortuantely is no way to store the Brueckner
> coefficients in a dump record. To use them in further
> calculations you have to add something like:
> 
> bccd;
> brueckner,2150.2
>  
> matrop;
> load,bo,square,2150.2
> save,bo,2160.1,orbitals
> dens,d,bo,"occupations"
> save,d,6000.2,density
> 
> into your input file. Note that noniterative triples
> have no effect on the orbital rotations.
> In case of MP2, however, there seems to be
> no other way than changing the code to keep
> the density matrix.
> Perhaps something like
> 
> c------------------------------------------
> c store MP2 density matrix
>       if(densav.gt.0) then
>         name=densav
>         ifil=(densav-name)*10.1
>         if(ifil.eq.0) ifil=2
>         length=ntdg
>         ni=0
>         call sudat(ifil,name,ni)
>         call reserve_dump(name,ifil,'CHARGE',length)
>         call write_den(q(idpos),0,'CHARGE')
>         call flush_dump
>         write(iout,1) name,ifil,dump_iset
>  1     format(/' Density matrix saved on  ',i8,'.',i1,
>      >    ' (density set',i2,')')
>       end if
> c---------------------------------------------
> 
> in "mp2dip.f" manages the problem.
> Best regards,
> 
> Andreas
> 
> 
> 
> ********************************************************* 
>  Andreas Hesselmann                                        
>  Institut fuer Theoretische Chemie                        
>  Heinrich-Heine Universitaet                              
>  Universitaetsstrasse 1 / 40225 Duesseldorf          
>  Phone:  +49-211 / 8111439                              
>  Fax:      +49-211 / 8113466                              
>  E-Mail:  andreas at theochem.uni-duesseldorf.de  
> *********************************************************
> 
> 
> 
> 
> 
> 
> 
>  
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- --
Prof. Hans-Joachim Werner
Institute for Theoretical Chemistry
University of Stuttgart
Pfaffenwaldring 55
D-70569 Stuttgart
Tel: (0049) 711 / 685 4400
Fax: (0049) 711 / 685 4442
email: werner at theochem.uni-stuttgart.de

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