Fragment key

Fragment (block-type)

Define a fragment. This key takes as argument the fragment file name (absolute path or path relative to the executing directory) and its contents are for each atom in the fragment two integers: atom number in the fragment versus atom number in this calculation. It has a subkey Labels so that you can assign meaningful names to the orbitals. You can define several fragments. Example

Fragment
  1 3 !  atom 1 of this fragment is assigned to third atom
  2 4 !  atom 2 of this fragment is assigned to fourth atom
  Labels
   Sigma
   Sigma*
   Pi_x
   Pi_y
   Pi_x*
   Pi_y*
  Subend
End

In this example the first four fragment orbitals will be labeled as stated in the body of this key. The remaining orbitals are labeled by the default labeling system (e.g. 1/FO/5, etc.). The labels are used in combination with options like Print Eigens and Print OrbPop. (See also Print OrbLabels).
This key can be given once for each fragment.