nopen for biradical singlet

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12:57:32 PM PST - Mon, Nov 5th 2012
According to the manual: NOPEN allow the user to specify the number of singly occupied orbitals for a particular calculation a biradical singlet is a singlet but has two singly occupied orbitals. is NOPEN 1 or 3? When i set nopen=1, the calculation directed me to a closed-shell singlet state, is it possible to find the biracial singlet? by setting nopen=3?

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2:19:30 PM PST - Mon, Nov 5th 2012
Tiechong You need to set nopen=1 and, at the same time, force the starting guess to get you towards the biradical singlet solution. You might want to have a look at an earlier posting(s) on this topic http://nwchemgit.github.io/Special_AWCforum/sp/id976 Please let us know if this addresses your problem. If this does not help, please send us more details about it. Cheers, Edo