.. _sphx_glr_api_gallery_md_constraints:

Constraints
------------

Rigid bond-length constraints enforced with the SHAKE algorithm, removing
fast bond vibrations from a molecular-dynamics trajectory.


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  <div id='sg-tag-list' class='sphx-glr-tag-list'></div>


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    <div class="sphx-glr-thumbnails">

.. thumbnail-parent-div-open

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    <div class="sphx-glr-thumbcontainer" tooltip="Ryckaert, Ciccotti, and Berendsen&#x27;s SHAKE algorithm (1977) replaces stiff bond springs by exact length constraints, restored after every Verlet position update by iterative corrections along the old bond vectors (~chemistrykit.md.systems.constraints.shake). A water-like triatomic is simulated twice: with stiff harmonic O-H springs (~chemistrykit.md.systems.pair_potentials.HarmonicMolecule), and with the two bonds held rigid by SHAKE (~chemistrykit.md.systems.constraints.ShakeMolecule), keeping the same flexible angle-bending term. Both runs use the same time step, chosen comfortably for the slow bending motion but too long for the fast bond stretch.">

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  .. image:: /api/gallery/md/constraints/images/thumb/sphx_glr_plot_01_shake_rigid_bonds_thumb.png
    :alt:

  :doc:`/api/gallery/md/constraints/plot_01_shake_rigid_bonds`

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      <div class="sphx-glr-thumbnail-title">SHAKE: rigid bonds let a bending molecule take larger time steps</div>
    </div>


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    </div>


.. toctree::
   :hidden:

   /api/gallery/md/constraints/plot_01_shake_rigid_bonds