Example: Compound Fragments: Ni(CO)4
************************************

"Download Frags_NiCO4.run"

   #! /bin/sh


   # An illustration of the fragment feature of ADF.

   # A transition metal complex is built from a Nickel atom and four CO fragments.
   # The outcomes allows for an analysis (of molecular orbitals and the Bonding
   # energy) in terms of the fragment properties. It is a Single Point calculation.
   # Geometry optimization would not have been possible in this set-up because an
   # optimization requires that only single-atom fragments are used.

   # == CO ==

   # The CO molecule, to serve as a fragment template in Ni(CO)4 , is computed from
   # the atomic fragments C and O. The coordinate values (atoms) are in bohr,
   # rather than in Angstrom because the unit-of-length is redefined by the key
   # units with subkey length.

   # The key scf is used to specify a somewhat tighter convergence criterion than
   # the default, just to illustrate how to do this (normal settings are quite
   # adequate).

   AMS_JOBNAME=CO $AMSBIN/ams <<eor
   System
     atoms [bohr]
        C   0  0  0
        O   0  0  2.15617844
     end
   end

   Task SinglePoint

   Engine ADF
     title CO (as fragment for NiCO4)
     eprint
       sfo eig ovl
     end
     basis
       core Small
       type DZ
     end
     scf
       converge 1e-8
     end
   EndEngine
   eor


   # One needs to include the subkey SFO of the key EPRINT with arguments eig and
   # ovl in order to get the SFO MO coefficients and SFO overlap matrix printed on
   # standard output.


   # == Main calculation ==


   # Apart from the title, the input contains comment. This does not specify
   # computational parameters but is only echoed in the output header, similar to
   # the title. Contrary to the title, however, such comments are not preserved,
   # apart from their echo in output and they are not written to adf.rkf or any
   # other result file.

   # The atomic coordinates (atoms) are given in bohr (Units).

   # The Atoms records contain also a specification of the fragments to which the
   # respective atoms belong: four different CO fragments. The Basis key is used
   # for the Ni atom, which implies that it is a fragment on its own.

   AMS_JOBNAME=NiCO4 $AMSBIN/ams <<eor
   System
     atoms [bohr]
        Ni   0.0          0.0           0.0
        C    2.0053211    2.0053211     2.0053211     adf.f=CO|1
        C   -2.0053211   -2.0053211     2.0053211     adf.f=CO|2
        C    2.0053211   -2.0053211    -2.0053211     adf.f=CO|3
        C   -2.0053211    2.0053211    -2.0053211     adf.f=CO|4
        O    3.2501913    3.2501913     3.2501913     adf.f=CO|1
        O   -3.2501913   -3.2501913     3.2501913     adf.f=CO|2
        O    3.2501913   -3.2501913    -3.2501913     adf.f=CO|3
        O   -3.2501913    3.2501913    -3.2501913     adf.f=CO|4
     end
   end

   Task SinglePoint

   Engine ADF
     title Ni(CO)4,  from fragments Ni and CO
     eprint
       sfo eig ovl
     end
     Basis
       PerAtomType Symbol=Ni File=$AMSRESOURCES/ADF/ZORA/TZP/Ni.2p
     End
     fragments
        CO  CO.results/adf.rkf
     end
   EndEngine
   eor
