[molpro-user] CCSD density matrix/natural orbitals

[Kirk Peterson]

Terry,

sorry, but I'm pretty sure Molpro only has a density matrix for closed-shell CCSD wavefunctions. Of
course you could always use CISD (with the CI directive, not CISD)...

regards,

Kirk

PS - btw, you could only do high spin systems anyway with the open-shell CCSD in Molpro. So the open
shell singlets would be a problem.

On Mar 10, 2010, at 4:41 PM, Terry Frankcombe wrote:

> Am I to take it from the deafening silence that no-one has any clue what
> I'm on about?
> 
> 
> On Thu, 2010-03-04 at 02:00 +1100, Terry Frankcombe wrote:
>> Hi folks
>> 
>> I'd like to calculate approximate natural orbitals for an open shell CCSD
>> wave function (triplet and open shell singlet states).  These would then
>> be used as starting orbitals for an MCSCF calculation.
>> 
>> The manual says no.  (Or at least says "only works for closed-shell MP2
>> and QCISD.)
>> 
>> However, I note that the MATROP facility can calculate natural orbitals
>> from a density matrix.  The manual also seems to suggest that I can't get
>> the density matrix, but there are some rather cryptic comments about
>> EXPEC,DM directives.  (All this is from the closed-shell CCSD section of
>> the manual anyway... the open-shell CCSD section of the manual is rather
>> bereft of details.)
>> 
>> Are there any back-door ways to convince molpro to give me open shell CCSD
>> natural orbitals/density matrices?  If so, can anyone point to some
>> fully-worked example code?
>> 
>> Regards
>> Terry
>> 
>> 
>> 
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