Open-Shell Total Energies

Posted by Yannis G. Lazarou on October 29, 2001 at 13:50:51:

Hello everybody!
Can anyone tell me if it is possible with MOLCAS 5 to
perform calculations on Open-Shell Species and get
meaningful results? I have recently tried to use MOLCAS
and I took some strange results:
The Hartree-Fock energies of open-shell species such as
H, C (triplet), F atoms and CH2F radical deviate by as
large as 0.14 a.u. (max. dev. for H and CH2F) from the
corresponding values by using Gaussian (with the
cc-pVTZ basis set in all cases and C1 symmetry).
In the MOLCAS manual (SCF program)it is explicitly
written that MOLCAS is not able to perform ROHF
calculations (neither UHF, I suppose...)
Since the HF step is required for the higher electron-
correlation level calculations (e.g. CCSD(T), MCPF),
are the resultant total correlated energies of
Open-Shell species meaningful?

Thanks in advance for any replies.

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• Re: Open-Shell Total Energies Per-Olof Widmark 15:56:31 10/29/01 (0) 130.235.29.69

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: Hello everybody! : Can anyone tell me if it is possible with MOLCAS 5 to : perform calculations on Open-Shell Species and get : meaningful results? I have recently tried to use MOLCAS : and I took some strange results: : The Hartree-Fock energies of open-shell species such as : H, C (triplet), F atoms and CH2F radical deviate by as : large as 0.14 a.u. (max. dev. for H and CH2F) from the : corresponding values by using Gaussian (with the : cc-pVTZ basis set in all cases and C1 symmetry). : In the MOLCAS manual (SCF program)it is explicitly : written that MOLCAS is not able to perform ROHF : calculations (neither UHF, I suppose...) : Since the HF step is required for the higher electron- : correlation level calculations (e.g. CCSD(T), MCPF), : are the resultant total correlated energies of : Open-Shell species meaningful? : Thanks in advance for any replies.