.. _18_k_points:

.. include:: ../../examples/18_k_points/README.rst

----

.. code-block:: python

   from eminus import Cell, SCF
   from eminus.units import ang2bohr
   

Create a diamond cell

:code:`kmesh=(2, 1, 1)` will create a Monkhorst-Pack k-point grid with two k-points

.. code-block:: python

   cell = Cell("C", "diamond", 30, ang2bohr(3.57), kmesh=(2, 1, 1))
   

One can also use a custom crystal basis, the diamond system would be equivalent of the following

.. code-block:: python

   # cell = Cell("C", "fcc", 30, ang2bohr(3.57), basis=[[0, 0, 0], [0.25, 0.25, 0.25]])
   

Do a DFT calculation for the cell

.. code-block:: python

   scf = SCF(cell)
   scf.run()
   

The :code:`SCF` and :code:`Atoms` objects have a k-point object

.. code-block:: python

   print(f"\nKPoints object\n{scf.kpts}\n")
   

The object can be modified, e.g., to create a non-Gamma-point centered mesh or to shift the k-points (do not forget to rebuild the object)

.. code-block:: python

   print(f"Original points:\n{cell.kpts.k}")
   cell.kpts.gamma_centered = False
   cell.build()
   print(f"non-Gamma-centered points:\n{cell.kpts.k}")
   cell.kpts.kshift = [1, 0, 0]
   cell.kpts.build()
   print(f"Shifted points:\n{cell.kpts.k}\n")
   

One can also use custom k-points

The easiest way to set them is the following

.. code-block:: python

   cell.set_k([[0, 0, 0]])
   SCF(cell, verbose=3).run()

Download :download:`18_k_points.py <../../examples/18_k_points/18_k_points.py>`