oqp.analysis.density_diff
=========================

.. py:module:: oqp.analysis.density_diff

.. autoapi-nested-parse::

   .. code-block:: text

      Attachment / detachment densities for MRSF excited states (unrelaxed).

      Given two roots ``i`` (reference state, default S0) and ``n``, the difference
      density is ``Delta = gamma^n - gamma^i``.  Because both state 1-RDMs share the
      same high-spin reference, the reference cancels and
      ``Delta = Delta gamma^n - Delta gamma^i`` (the two exposed traceless diagonal
      blocks).  Diagonalizing the symmetric ``Delta`` (in the orthonormal MO basis)
      and splitting by eigenvalue sign yields the detachment (negative) and
      attachment (positive) densities of Head-Gordon et al.



Functions
---------

.. autoapisummary::

   oqp.analysis.density_diff.attachment_detachment


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

.. py:function:: attachment_detachment(states, n, ref=0)

   .. code-block:: text

      Unrelaxed attachment/detachment analysis for the ref -> n transition.

      Returns A, D (AO-basis density matrices), the natural orbitals/occupations,
      and the promotion number n_promoted = Tr(A) = Tr(D).