httk.atomistic.sites
====================

.. py:module:: httk.atomistic.sites

.. autoapi-nested-parse::

   The Sites class for httk-atomistic.



Classes
-------

.. autoapisummary::

   httk.atomistic.sites.Sites


Module Contents
---------------

.. py:class:: Sites(reduced_coords: httk.core.VectorLike)

   The sites of a crystal structure: the Nx3 matrix of reduced coordinates, held **exactly**.

   Reduced (fractional) coordinates are the symmetry-native frame: point-group operations are
   integer matrices and translations are rationals, so no radicals ever appear. They are therefore
   stored as an exact rational :class:`~httk.core.FracVector` of shape ``(N, 3)``. A Sites object
   is iterable and indexable over its length-3 coordinate rows (each a ``FracVector``), with
   ``len`` giving the number of sites.

   Inputs embed exactly: rationals (and rational-valued floats), rational strings, and numpy arrays
   all land on their exact rational value. An irrational :class:`~httk.core.SurdVector` input is
   reduced deterministically through the vector family's ``fractions`` hub (never raising on data);
   the exact Cartesian frame — where radicals belong — is obtained instead via
   :meth:`~httk.atomistic.Structure.cartesian_sites`.


   .. py:property:: reduced_coords
      :type: httk.core.FracVector


      The Nx3 reduced site coordinates as an exact ``FracVector`` (one site per row).


   .. py:method:: numeric() -> httk.atomistic.numeric_sites.NumericSites

      A plain-numpy presentation of these sites (requires the ``httk-atomistic[numpy]`` extra).