[molpro-user] UMP2/uhf for natrual orbitals

Tatiana Korona tania at tiger.chem.uw.edu.pl
Tue Mar 18 12:41:51 GMT 2014

Dear Joachim,

One can however install a program of Mihaly Kallay (MRCC), which is interfaced 
with MOLPRO. This program uses both alpha and beta orbitals if UHF is performed 
before calling it (of course it is not as effective as Molpro-CCSD:-).

Best wishes,


On Mon, 17 Mar 2014, Hans-Joachim Werner wrote:

> See manual, section "16.1.5 Special options for UHF calculations". If UHF  natural orbitals are used
> as starting guess for multi, it determines the active space using the occupation number thresholds UNOMIN, UNOMAX.
> This happens by default if multi follows an UHF calculation.
> This behaviour can be overwritten by the usual „occ" and „closed" directives. UMP2 is a poor method if
> spin-contamination is strong and should in my opinion not be used. Unfortunately, we do currently not
> have uccsd based on uhf orbitals.
> Best regards
> Joachim Werner
> ---
> Prof. Dr. Hans-Joachim Werner
> Institut for Theoretical Chemistry
> University of Stuttgart
> Pfaffenwaldring 55
> D-70569 Stuttgart
> Tel: +49 711 / 685 64400
> Fax: +49 711 / 685 64442
> email: werner at theochem.uni-stuttgart.de
> Am 17.03.2014 um 08:47 schrieb Bo Long <wwwltcommon at sina.com>:
>> Dear Prof Werner:
>>   I am so sorry to interrupt you. I face some situations in which wavefunction can not be well described using rmp2 based on rhf. I want to do UMP2 based on UHF. I do not know whether CASSCF calculation can read natural orbital from the previous UMP2/UHF? Thank you for your help.
>> Best Wishes
>> Bo Long
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Dr. Tatiana Korona http://tiger.chem.uw.edu.pl/staff/tania/index.html
Quantum Chemistry Laboratory University of Warsaw, Pasteura 1, PL-02-093 Warsaw, POLAND

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