Gaussian
========

Overview
--------
Low-level Gaussian shell and primitive types are exposed under
``libintx.data``. These objects are intended for development or for
manually constructing basis sets without relying on PySCF conversion helpers.

Key points:

* ``Gaussian(l, ex, cc, pure=True)`` - constructor with angular momentum ``l``, exponent list ``ex`` and contraction coefficients ``cc``.
* Properties: ``K`` (contraction degree), ``L`` (angular momentum), ``pure``, ``ncart``, ``nspher``, ``nao``, ``normalization_factor``.
* Methods: ``normalized(racah=True)`` - return normalized shell.

Primitive:
----------
* Primitive is a POD class with attributes ``a`` (exponent) and ``c`` (coefficient).

Example
-------
.. code-block:: python

   g = libintx.data.Gaussian(l=0, ex=[1.0, 0.5], cc=[0.6, 0.4], pure=True)
   atom = libintx.data.Atom([0.0, 0.0, 0.0])
   basis = libintx.Basis([g], [[0.0,0.0,0.0]]).normalize()