Example: Unpaired electrons cyclobutadiene¶

#!/bin/sh

$AMSBIN/ams << eor

Task SinglePoint

Properties
   Gradients true
End

System
    Atoms
        C         0.73022709  0.73022709  0.00000000
        C        -0.73022709  0.73022709  0.00000000
        C        -0.73022709 -0.73022709  0.00000000
        C         0.73022709 -0.73022709  0.00000000
        H         1.50475790  1.50475790  0.00000000
        H        -1.50475790  1.50475790  0.00000000
        H        -1.50475790 -1.50475790  0.00000000
        H         1.50475790 -1.50475790  0.00000000
    End
End

Engine DFTB
   Model SCC-DFTB
   ResourcesDir DFTB.org/mio-1-1
   SCC
      Iterations 200
      Unrestricted Yes
   End
   Occupation Strategy=aufbau
   UnpairedElectrons 2
EndEngine

eor