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Wenli Zou
qcband@gmail.com

Please let me copy the following sentences from my paper J. Chem. Phys. 130, 154313, 2009 (with some modifications) to explain the advantages and disadvantages of SA-MCSCF.

If proper states are selected, the state-averaging method can be used to maintain the required degeneracy of the relevant states, to describe the ground and excited states in balance, and to avoid artifactual symmetry breaking. However, the state-averaged method often fails to give a balanced description if the states have different occupations in 3d or Rydberg orbitals. This is the so-called orbital bias problem, i.e., the orbitals are biased in favor of several of the states.

To the best of my knowledge, this was first summarized by Bauschlicher et. al. (Ref. 20 therein). Hope it will help.

Best regards,
Wenli

On Mon Oct 8 '12 6:33pm, Patrick SK Pang wrote
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>Dear all,

>What are the merits and drawbacks of using state averaging in MCSCF calculation? Similarly, What are the merits and drawbacks of MCSCF calculaton without state averaging?

>Thanks!

>Patrick