.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "gallery/plot_qpbands_with_scissor.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        Click :ref:`here <sphx_glr_download_gallery_plot_qpbands_with_scissor.py>`
        to download the full example code or to run this example in your browser via Binder

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_gallery_plot_qpbands_with_scissor.py:


GW with scissors operator
=========================

This example shows how to generate an energy-dependent scissors operator
by fitting the GW corrections as function of the KS eigenvalues.
We then use the scissors operator to correct the KS band structure
computed on a high symmetry k-path. Finally, the LDA and the QPState band
structure are plotted with matplotlib.

.. GENERATED FROM PYTHON SOURCE LINES 12-64



.. rst-class:: sphx-glr-horizontal


    *

      .. image:: /gallery/images/sphx_glr_plot_qpbands_with_scissor_001.png
          :alt: plot qpbands with scissor
          :class: sphx-glr-multi-img

    *

      .. image:: /gallery/images/sphx_glr_plot_qpbands_with_scissor_002.png
          :alt: plot qpbands with scissor
          :class: sphx-glr-multi-img

    *

      .. image:: /gallery/images/sphx_glr_plot_qpbands_with_scissor_003.png
          :alt: Silicon band structure
          :class: sphx-glr-multi-img

    *

      .. image:: /gallery/images/sphx_glr_plot_qpbands_with_scissor_004.png
          :alt: Silicon band structure, LDA, LDA+scissors(e)
          :class: sphx-glr-multi-img


.. rst-class:: sphx-glr-script-out

 Out:

 .. code-block:: none

    KS fermie 5.598313017568332 eV --> QP fermie 5.40710713209731 eV Delta(QP-KS)= -0.1912058854710219 eV
    KS fermie 5.598453325290463 eV --> QP fermie 5.407251265916601 eV Delta(QP-KS)= -0.19120205937386192 eV






|

.. code-block:: default

    import abipy.data as abidata
    from abipy.abilab import abiopen, ElectronBandsPlotter

    # Get the QP results from the SIGRES.nc database.
    sigma_file = abiopen(abidata.ref_file("si_g0w0ppm_nband30_SIGRES.nc"))

    # Let's have a look at the QP correction as function of the KS energy.
    # Don't shift KS eigenvalues to have zero energy at the Fermi energy.
    # because we need the absolute values for the fit.
    # The qpeme0(e0) curve consists of two branches:
    #   the one in the [-6, 5.7] eV interval associated to valence states
    #   and the one in the [6.1, 15] eV interval associated to conduction bands.
    # We will fit these results with 2 functions defined in these two domains.
    sigma_file.plot_qps_vs_e0(e0=None)
    sigma_file.plot_qps_vs_e0()

    qplist_spin = sigma_file.qplist_spin

    # Define the two domains and construct the scissors operator
    domains = [[-10, 6.1], [6.1, 18]]
    scissors = qplist_spin[0].build_scissors(domains, bounds=None)

    # Read the KS band energies computed on the k-path
    ks_bands = abiopen(abidata.ref_file("si_nscf_GSR.nc")).ebands

    # Read the KS band energies computed on the Monkhorst-Pack (MP) mesh
    # and compute the DOS with the Gaussian method
    ks_mpbands = abiopen(abidata.ref_file("si_scf_GSR.nc")).ebands
    ks_edos = ks_mpbands.get_edos()

    # Apply the scissors operator first on the KS band structure
    # along the k-path then on the energies computed with the MP mesh.
    qp_bands = ks_bands.apply_scissors(scissors)

    qp_mpbands = ks_mpbands.apply_scissors(scissors)

    # Compute the DOS with the modified QPState energies.
    qp_edos = qp_mpbands.get_edos()

    # Plot the LDA and the QPState band structure with matplotlib.
    plotter = ElectronBandsPlotter()

    plotter.add_ebands("LDA", ks_bands, edos=ks_edos)
    plotter.add_ebands("LDA+scissors(e)", qp_bands, edos=qp_edos)

    # By default, the two band energies are shifted wrt to *their* fermi level.
    # Use e=0 if you don't want to shift the eigenvalus
    # so that it's possible to visualize the QP corrections.
    plotter.combiplot(title="Silicon band structure")

    plotter.gridplot(title="Silicon band structure")
    sigma_file.close()


.. rst-class:: sphx-glr-timing

   **Total running time of the script:** ( 0 minutes  1.888 seconds)


.. _sphx_glr_download_gallery_plot_qpbands_with_scissor.py:


.. only :: html

 .. container:: sphx-glr-footer
    :class: sphx-glr-footer-example


  .. container:: binder-badge

    .. image:: images/binder_badge_logo.svg
      :target: https://mybinder.org/v2/gh/abinit/abipy/gh-pages?filepath=notebooks/gallery/plot_qpbands_with_scissor.ipynb
      :alt: Launch binder
      :width: 150 px


  .. container:: sphx-glr-download sphx-glr-download-python

     :download:`Download Python source code: plot_qpbands_with_scissor.py <plot_qpbands_with_scissor.py>`



  .. container:: sphx-glr-download sphx-glr-download-jupyter

     :download:`Download Jupyter notebook: plot_qpbands_with_scissor.ipynb <plot_qpbands_with_scissor.ipynb>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_