[molpro-user] How to generate modified virtual orbitals (MVOs)

[John Sears]

To my knowledge, MVO's are not implemented into Molpro. It should in
principle be possible to generate these with the matrix operation facilities
provided by molpro, but this would be fairly involved. My suggestion, if you
are only needing starting orbitals for CAS computations would be to use the
natural orbitals from a CISD or MP2 computation. MP2 and CI natural orbitals
have been shown to be good substitutes for CASSCF orbitals and have provided
reasonable starting orbitals in my experience (much better than the UHF
NO's). Another thing that often helps in difficult cases it to pre-converge
the CAS with a small (STO-3G) basis and use these to start the CAS in a
larger basis. Hope this helps.
Regards
John


On 6/25/08 6:07 PM, "zhendong zhao" <zzhao at olemiss.edu> wrote:

> Hi Molpro users,
> I just began learning molpro. I always have some newbie problems.
> Currently I want  generating modified virtual orbitals (MVOs), which
> will give more valence-like LUMOs, and it is easier for me to select MOs
> for CAS calculations. Is it possible in MOLPRO? If possible, could you
> attach an example input file?
> Thanks in advance,
> 
> ZZ

-- 
John S. Sears
Post-Doctoral Research Associate
Center for Computational Molecular Science and Technology
Center for Organic Photonics and Electronics
School of Chemistry and Biochemistry
Georgia Institute of Technology
Atlanta, GA 30332-0400
Office: MS&E 4202 O
Phone: (678) 416-0362
Email: john.sears at chemistry.gatech.edu