Gaussian09
==========

Gaussian09 is coupled to the :mod:`metafalcon` package by a text-based interface and can be used for
semiempirical AM1, DFT or CASSCF calculations. Similar to the :doc:`Molpro <molpro>` interface,
`head` and `tail` files are used to build the input for Gaussian.

For a simple AM1 calculation, the `head` file looks like::

    #p am1

    Title

    0 1

The `tail` file only contains a blank line that will be inserted by the dynamics program after
the molecular geometry.

The keywords `fchk`, `nosymm` and `force` are added automatically because they are needed for the
evaluation of the outputs.

Gaussian is used, if the following information is provided in the `meta-config.json` file under the
``"molecular dynamics"`` keyword::

    "interface": {
      "type": "g09",
      "configure": {}