Exclude or restrict elements

generation:
  exclude_elements: [Pb, Cd, Hg]           # never used, on any site
  only_elements:                           # restrict a site group to a shortlist
    B: [Ti, Zr, Hf, Sn]

Both are applied to the family before the search starts, so the decoder cannot even propose an excluded element. The Studio's element chips do the same thing (click to toggle) and show the counts change.

To change which elements a family allows at all, or their oxidation states, copy the family file and edit the groups: section — see Change the material family.