Re: how to define the charge

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Posted by Per-Olof Widmark on January 23, 2002 at 09:46:43:

In Reply to: how to define the charge posted by glen on January 21, 2002 at 09:23:18:

You can only use the scf program for closed shells. If your system contains an odd
number of electrons (as a neutral species) you can do the anion or cation. In this
case you can specify the charge with keyword "charge", then the aufbau principle
will be used to determine the occupation per irrep. As an alternative you can use
the keyword "occupied" to specify the population per irrep. The latter normally
converges faster and is better if you know how the orbitals are populated.

If you want to treat a system with an odd number of electrons you need to use the
rasscf program and specify an active space such that you get an open shell scf

: I want to calculate a anion or cation.Is it necessary to define the charge in SCF section? If I used the Keywore 'charge',how I can define the occupied? Any tips will be appreciated!

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