Spartan tip – Symmetry errors

Spartan automatically examines models for symmetry. When it finds symmetry elements, it applies these in subsequent calculations. For example, if you build ‘flat’ NH3 (possible point groups: Cs, C3v, D3h, etc.) and calculate its equilibrium geometry, you will end up with a flat ‘minimum’. In other words, your final model won’t be a minimum at all. Here are some tips for dealing with symmetry, wanted and unwanted:

  • turning off symmetry constraints
    • uncheck the Symmetry box in Setup: Calculations
    • adjust an atom (or group) position so that the initial model is less symmetric (if Spartan lists the point group as C1, no symmetry has been detected)
  • “<point group> slipped through” error message prevents the desired calculation – either uncheck the Symmetry box (see above) or Minimize a few times to reach a higher symmetry model (this can be a disaster so remember that you can use Undo to reverse one Minimize)
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