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.eigval — Exciton Energies
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This file contains the exciton eigenvalues (binding energies) computed from solving the Bethe-Salpeter Equation (BSE).

It is generated when running `Xatu` with an exciton input file and requesting eigenvalues explicitly (via ``-e`` or ``--energy``).

Format
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A plain text list of exciton energies in **electron volts (eV)**:

.. code-block:: text

   Ncells
   BSE dimension
   Number of states
   E_1
   E_2
   E_3
   E_4
   .
   .
   .

Each line corresponds to a different exciton state, in ascending order of energy.