podcoupling
***********
Electronic coupling between two covalently bonded fragments of one converged ground-state DFT calculation, by projection-operator diabatization (POD2): each fragment's Fock sub-block is diagonalized separately and the coupling is read from the off-diagonal block, with the Lowdin correction for the overlap of the two fragment orbitals (as in DIPRO, Baumeier et al., PCCP 12, 11103 (2010)). For non-bonded fragments use the coupling tool (DIPRO).
The following table contains the defaults input options for the calculator, The default `OPTIONAL` means this option is switched off, if no input is given. 
`REQUIRED` arguments have to be specified, otherwise an error is thrown.

.. list-table::
   :header-rows: 1
   :widths: 30 20 15 15
   :align: center

   * - Property Name
     - Default Value
     - Description
     - Valid Input
   * - job_name
     - system
     - | Input file name without extension, also used for intermediate
       | files
     - 
   * - orb_file
     - system.orb
     - | Converged ground-state DFT calculation (orb file) of the
       | bonded supermolecule
     - 
   * - fragment_A
     - 
     - | Atom indices (0-based) of fragment A, e.g. '0:5' or '0
       | 1 2 3 4 5' (same syntax as cdft.indices)
     - 
   * - fragment_B
     - 
     - | Atom indices (0-based) of fragment B, disjoint from fragment_A
       | 
     - 
   * - levA
     - 1
     - | Number of occupied and of virtual orbitals of fragment
       | A, counted from the HOMO/LUMO gap (as levA of the coupling
       | tool): 1 covers HOMO and LUMO, 2 covers HOMO-1 to LUMO+1,
       | etc.
     - int+
   * - levB
     - 1
     - As levA, for fragment B
     - int+
   * - write_cube_files
     - false
     - | Write a cube file for each fragment orbital covered by
       | levA/levB
     - bool
   * - xsteps
     - 25
     - Grid points in x for the cube files (as in gencube)
     - int+
   * - ysteps
     - 25
     - Grid points in y for the cube files (as in gencube)
     - int+
   * - zsteps
     - 25
     - Grid points in z for the cube files (as in gencube)
     - int+
   * - padding
     - 6.5
     - Distance of the cube grid from the molecule (as in gencube)
     - float+
.. note::
   An *xml* file containing the defaults for the `podcoupling` calculator can be created via `-p podcoupling -o FILENAME` command line options `