*****
DFTB+
*****

.. py:class:: DFTBplus

This interface supports energy and gradient evaluations with the
`DFTB+ <https://dftbplus.org/>`_ semi-empirical electronic structure package
(v20 or later).

A DFTB+ :ref:`Theory <theories>` object can be specified as follows::

  my_frag = Fragment(...)

  my_theory = DFTBplus(frag=my_frag,
                       ...)

which would then be called as ``theory=my_theory`` in subsequent tasks (see :ref:`Tasks <tasks>`).

Note that as it is a semi-empirical code, the DFTB+ interface will ignore
some keyword options that are common to other QM interfaces, such as
``basis``, ``ecp``, ``functional``, etc.


General options
===============

.. py:attribute:: scc

   (default: ``True``) Use the Self-Consistent-Charge (SCC-DFTB) method.

.. py:attribute:: skf_path

   (default: ``''``) Path to directory holding Slater-Koster files


SCF options
===========

.. py:attribute:: maxcyc

   (default: ``100``) Maximum SCC iterations allowed if using SCC-DFTB