I have run some calculations to analyse the occupation of natural orbitals. Since it is needed to run in triplet state, I get two orbitals with occupation number 1. Now, which orbital occupation number is to be taken as the occupation number of lowest unoccupied natural orbital as it is needed to define the diradical character in the system ?

  • $\begingroup$ Why would the degeneracy in occupied orbitals raise any ambiguities for the unnocupied orbitals? $\endgroup$ – Feodoran Dec 20 '18 at 8:11
  • $\begingroup$ I am facing issue in defining it. The reported values and that from my calculations do not match. May be my procedure is wrong but I am not able to identify where is the fault. @Feodoran $\endgroup$ – juno Dec 20 '18 at 11:00
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    $\begingroup$ I don't know what values you are talking about, but if you have two singly occupied orbitals (SOMO), then the LUMO should be the one next lowest in energy. For natural orbitals it probably has some occupation number slightly larger than 0. But I am not aware of any strict definition here. $\endgroup$ – Feodoran Dec 20 '18 at 11:54
  • $\begingroup$ thank you @Feodoran that is also my line of thought but then my diradical character values are not matching with the reported values (e.g. for polyacenes) $\endgroup$ – juno Dec 20 '18 at 14:01

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