Question about cdft spin specification

[Jae Eun Lee]

Hi, I would like to ask a question regarding spin restriction in cdft.

I am running a simple cdft calculation with ethylene dimer and I am trying to restrict the spin of negative ethylene monomer to alpha.

I am confused about how to specify the spin of an alpha unpaired electron. should the input be like

cdft 1 6 spin 0.5

or

cdft 1 6 spin 1.0

Based on my chemistry intuition, spin should be 0.5 but I am not sure how nwchem cdft is coded. Could you please clarify this for me? it was not really explained neither on github nor forum.

p.s. spin 1 comes from one of the codes written by Jarvist. Here is the link : https://gist.github.com/jarvist/4673243

Thank you so much for the help!

Here is my input and I have highlighted the cdft spin part in bold:

echo

start ethylene_dimer_cdft_reactant

title "ethylene_dimer_cdft_reactant"

memory total 36000 mb

geometry "dimer" units angstroms print xyz noautosym nocenter

    C                 -0.01379224    0.04989615   -0.00064395

    H                  0.91594156   -0.47972168   -0.00064395

    H                 -0.93732164   -0.49046802   -0.00064395

    C                 -0.02165037    1.40507337   -0.00064395

    H                 -0.95138417    1.93469121   -0.00064395

    H                  0.90187903    1.94543754   -0.00064395

    C                  0.02682413    0.02023460    1.99872358

    H                  0.95655793   -0.50938323    1.99872358

    H                 -0.89670527   -0.52012957    1.99872358

    C                  0.01896600    1.37541182    1.99872358

    H                 -0.91076780    1.90502966    1.99872358

    H                  0.94249540    1.91577599    1.99872358

end

basis

  * library 6-31G**

end

driver

  maxiter 100

  TIGHT

  XYZ

end

set geometry "dimer"

charge -1

dft

  xc b3lyp

  mult 2

  direct

  iterations 100

  convergence density 1e-8

  convergence energy 1e-8

  convergence nolevelshifting

  print "final evals" "final vectors"

  grid xfine

  odft

  cdft 1 6 charge -1.0

  cdft 1 6 spin 0.5 or 1.0 # should it be 0.5 or 1 to just have an alpha unpaired e-?

  cdft 7 12 charge 0.0

  cdft 7 12 spin 0.0

  vectors output ethylene_dimer_cdft_reactant.movecs

end

set dft:cdft_maxiter 1000

task dft optimize

~