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Re: Need help regarding using Symmetry and mulitplicity both..

Alex Granovsky
gran@classic.chem.msu.su


Dear Siddheshwar,

>1) I understand when RHF is used and when ROHF.. Now could anyone clarify:
>TO MAKE EVEN NO. OF ELECTRONS (assuming the system has odd no. of electrons) IN SYSTEM, I CAN EITHER ADD +1 OR -1 CHARGE USING icharg...  (FOR RHF)
>SECOND WAY I CAN ALSO CHANGE THE MULTIPLICITY OF THE SYSTEM AND RUN ROHF... BUT BY DOING THIS I HAVE ADDED A SPIN TO THE SYSTEM..
>Please tell me... Are not both ways same?? Don't both the ways mean that I have added an electron?


1) Normally, there should be some physical or chemical ground (a model)
behind your QC computations. This model defines what should the
appropriate multiplicity and the overall charge be.

>2) I was running RHF on of such cluster with C1 symmetry and even no. of electrons. It worked well. But when I added symmetry to the i/p file and added ONLY the symmetry atoms, then I got errors: a) ODD no. of electrons. Cant run RHF  and b) too many primitive bend coordinates. For around 70 atoms in total (with C1)
>How should I go about this problem now? I want to use symmetry in my case.

2) This means you have made some errors in your input file.

Kind regards,
Alex Granovsky

On Mon Feb 10 '14 2:53pm, Siddheshwar Chopra wrote
--------------------------------------------------
>Dear Sir,
>I am stuck with some doubts and not able to get them clarified at all. They are::

>Say I have a CxHyMetal cluster...


>Please help.
>
>
>


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