restricted open-shell Kohn-Sham (ROKS) Setup

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Michael LaCount

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Aug 25, 2025, 1:28:04 AM (12 days ago) Aug 25
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Hello I am trying to set up a fairly simple test run for ROKS. The simplest test I could think of for what I want to try to do is to set up 2 jobs, both will have a Na and Cl atom placed 1nm apart and with periodic boundary conditions turned off (and 1nm from nearest box wall). The 2 jobs differ in that I want the first to converge to neutral atoms, and the second to converge to ions. My understanding with ROKS is that this should be doable and fairly easy.

My jobs are running into an error. CPASSERT failed qs_ks_utils.F:263, so there is something wrong with my setup. The CPASSERT in question is:
      CPASSERT(Nelectron == k_alpha - k_beta)
The CP2K code block I am using is:

  &DFT
    CHARGE 0
    MULTIPLICITY 1
    UKS
    ROKS
    &LOW_SPIN_ROKS
      ENERGY_SCALING 1 -1 1 -1
      SPIN_CONFIGURATION 1 1
      SPIN_CONFIGURATION 1 2
      SPIN_CONFIGURATION 2 2
      SPIN_CONFIGURATION 2 1
    &END LOW_SPIN_ROKS
...
 &END DFT

My interpretation of how this would work is that it would find 2 unpaired electron levels: an 's' for Na and a 'p' for Cl. This would then bias the two orbitals to a certain spin. I don't think I am understanding the syntax of these commands properly and would like some guidance on how to properly cover the 2 scenarios I mentioned (neutral Na/Cl and ionic Na/Cl in a non-periodic box).

Thanks
Michael
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