basinfo
=======

This option defines the implementation details of basis functions.

.. contents::
   :local:

.. option:: angular_type

   .. list-table::
      :stub-columns: 1
      :widths: 5 20
   
      * - Value
        - ``Cartesian``. Will use Cartesian basis sets, i.e. :math:`6d/10f/15g\cdots`
      * - 
        - ``spherical``. Will use the spherical basis sets, i.e. :math:`5d/7f/9g\cdots`
      * - Default
        - ``spherical``
      
   Decide whether to use spherical or Cartesian GTO basis set. Usually, there is no need to use Cartesian GTO basis sets except for test purpose.

.. option:: linear_dependence

   .. list-table::
      :stub-columns: 1
      :widths: 5 20
   
      * - Value
        - A real number
      * - Default
        - ``1.E-8``
   
   Assign the threshold that admits the linear dependence of the basis set. It should be a positive real number. When linear dependence is detected, Qbics will stop the calculation. 

.. option:: ghost

   .. list-table::
      :stub-columns: 1
      :widths: 5 20
   
      * - Value
        - Atom range
      * - Default
        - None
   
   Assign "ghost atoms", which means that those atoms defined in ``mol ... end`` have basis functions, but nuclear and electrons disappear.

   This is often used for some special purposes, like basis set superposition error (BSSE) calculations, although Qbics can automatically do this. 

   For example, the following input:

   .. code-block:: bash
    :linenos:

    basis
      def2-SVP   
    end
    basinfo
      ghost 1-3 6 9-11 # Set ghost atoms.
    end
    mol # Due to the use of ghost, there are actually only 13-7=6 real atoms.
      C                 -1.72885348   -0.27751594   -0.54883607
      C                 -0.54335149   -0.47251267    0.35111257
      C                 -1.54903120    0.59933911    0.65616163
      H                 -1.57461433    0.15313436   -1.55374643
      H                 -2.53379418   -1.03326873   -0.54728357
      H                 -0.50081907   -1.36760843    0.99612354
      H                 -2.22562112    0.47045579    1.51913545
      H                 -1.26635100    1.65697053    0.51257787
      C                  0.85387745   -0.06614383   -0.15308545
      O                  1.09143365    0.21649289   -1.34006650
      N                  1.82735682   -0.03716326    0.80612988
      H                  2.75631019    0.21299272    0.57405353
      H                  1.62607490   -0.26347660    1.74464638
    end

   The ``ghost`` keyword indicates that in the following calculations, there will be basis functions for atom 1,2,3,6,9,10,11, but the atoms, i.e., the nuclei and electrons, are not present, disappeared like ghosts.