open-shell singlet

[Martijn Zwijnenburg]

Hi Edo, Niri & everyone else,

A student of mine is attempting to converge to an open-shell singlet using NWChem 6.8 for a small transition metal containing complex but all attempts fail and the calculations converge to the closed-shell singlet instead. She uses odft, mult 1 and our starting structure lacks symmetry.

I found some references on how to fix this issue in the old NWChem forum but sadly the links to the input files there are broken. These forum posts also refer to using "set mixang xx", where xx is a number, but I cannot find any reference to mixang in the current manual.

What is the best approach to finding an open-shell singlet with NWChem?

Thanks in advance,

Martijn

[Edoardo Aprà]

The undocumented  'set mixang' option might work, but I would rather suggest using the Fragment Guess option if you can identify fragments in your molecule where spin polarization of opposite sign is likely to appear.

This approach has been discussed in the following forum entries

https://nwchemgit.github.io/Special_AWCforum/st/id1680/DFT_Broken-symmetry_for_molecule....html

https://groups.google.com/g/nwchem-forum/c/O9c5I9-Y3a0/m/NCopezbACwAJ