.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "api/gallery/crystal/lattice_energy/plot_03_shannon_ionic_radii.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

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

        :ref:`Go to the end <sphx_glr_download_api_gallery_crystal_lattice_energy_plot_03_shannon_ionic_radii.py>`
        to download the full example code.

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

.. _sphx_glr_api_gallery_crystal_lattice_energy_plot_03_shannon_ionic_radii.py:


Shannon's effective ionic radii: additivity and periodic trends
=================================================================

Shannon (1976) fitted one self-consistent radius per ion (for a given
coordination number) so that cation-anion distances in thousands of
crystals are reproduced by simple sums :math:`r_++r_-`.
``SHANNON_IONIC_RADII_PM`` holds the 6-coordinate values; here their sums
are checked against measured rock-salt nearest-neighbor distances, and
their periodic trends are plotted.

.. GENERATED FROM PYTHON SOURCE LINES 14-37

.. code-block:: Python

    import matplotlib.pyplot as plt

    from chemistrykit.crystal.utils.reference_data import SHANNON_IONIC_RADII_PM as R

    measured_r0 = {  # rock-salt nearest-neighbor distances, pm
        ("Li+", "F-"): 201.0,
        ("Na+", "F-"): 232.0,
        ("Na+", "Cl-"): 282.0,
        ("K+", "Cl-"): 315.0,
        ("K+", "Br-"): 330.0,
        ("Rb+", "I-"): 367.0,
        ("Mg2+", "O2-"): 211.0,
        ("Ca2+", "O2-"): 240.0,
    }
    sums, measured, labels = [], [], []
    for (cat, an), r0 in measured_r0.items():
        s = R[cat] + R[an]
        sums.append(s)
        measured.append(r0)
        labels.append(f"{cat.rstrip('+2')}{an.rstrip('-2')}")
        print(f"{cat:5s}+{an:4s} r+ + r- = {s:6.1f} pm   measured r0 = {r0:6.1f} pm   ({(s - r0) / r0:+.1%})")
        assert abs(s - r0) / r0 < 0.05





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

 .. code-block:: none

    Li+  +F-   r+ + r- =  209.0 pm   measured r0 =  201.0 pm   (+4.0%)
    Na+  +F-   r+ + r- =  235.0 pm   measured r0 =  232.0 pm   (+1.3%)
    Na+  +Cl-  r+ + r- =  283.0 pm   measured r0 =  282.0 pm   (+0.4%)
    K+   +Cl-  r+ + r- =  319.0 pm   measured r0 =  315.0 pm   (+1.3%)
    K+   +Br-  r+ + r- =  334.0 pm   measured r0 =  330.0 pm   (+1.2%)
    Rb+  +I-   r+ + r- =  372.0 pm   measured r0 =  367.0 pm   (+1.4%)
    Mg2+ +O2-  r+ + r- =  212.0 pm   measured r0 =  211.0 pm   (+0.5%)
    Ca2+ +O2-  r+ + r- =  240.0 pm   measured r0 =  240.0 pm   (+0.0%)




.. GENERATED FROM PYTHON SOURCE LINES 38-56

.. code-block:: Python

    fig, axes = plt.subplots(1, 2, figsize=(11, 4))
    alkali = ["Li+", "Na+", "K+", "Rb+", "Cs+"]
    halide = ["F-", "Cl-", "Br-", "I-"]
    axes[0].plot(range(len(alkali)), [R[i] for i in alkali], "o-", label="alkali cations (M+)")
    axes[0].plot(range(len(halide)), [R[i] for i in halide], "s-", label="halide anions (X-)")
    axes[0].set_xticks(range(5), ["period 2", "3", "4", "5", "6"])
    axes[0].set_ylabel("Shannon radius, CN 6 (pm)")
    axes[0].set_title("Radii grow down a group")
    axes[0].legend()
    axes[1].scatter(measured, sums)
    for label, x, y in zip(labels, measured, sums, strict=True):
        axes[1].annotate(label, (x, y), textcoords="offset points", xytext=(5, -10))
    axes[1].plot([190, 380], [190, 380], "k--", lw=0.8)
    axes[1].set_xlabel("measured r0 (pm)")
    axes[1].set_ylabel(r"Shannon $r_+ + r_-$ (pm)")
    axes[1].set_title("Additivity of Shannon radii")
    plt.tight_layout()
    plt.show()



.. image-sg:: /api/gallery/crystal/lattice_energy/images/sphx_glr_plot_03_shannon_ionic_radii_001.png
   :alt: Radii grow down a group, Additivity of Shannon radii
   :srcset: /api/gallery/crystal/lattice_energy/images/sphx_glr_plot_03_shannon_ionic_radii_001.png
   :class: sphx-glr-single-img






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

   **Total running time of the script:** (0 minutes 0.070 seconds)


.. _sphx_glr_download_api_gallery_crystal_lattice_energy_plot_03_shannon_ionic_radii.py:

.. only:: html

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

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