.. _20_smeared_occupations:

.. include:: ../../examples/20_smeared_occupations/README.rst

----

.. code-block:: python

   from eminus import Cell, RSCF
   from eminus.tools import get_Efermi
   from eminus.units import ha2kelvin
   

Create a cell for an aluminum crystal

Set a smearing value in atomic units

The resulting SCF will use a Fermi-Dirac function to smear the occupations over the selected bands

.. code-block:: python

   cell = Cell("Al", "fcc", ecut=10, a=7.63075, bands=6, smearing=0.01)
   

Create the SCF object

The occupations update per SCF cycle can be controlled with the :code:`smear_update` parameter

.. code-block:: python

   scf = RSCF(cell, etol=1e-5, verbose=0)
   scf.smear_update = 1
   

Do the DFT calculation

.. code-block:: python

   scf.run()
   

The resulting total energy includes an entropic term when smearing is enabled

.. code-block:: python

   print(scf.energies)
   

We can extrapolate the energy to T=0

.. code-block:: python

   print(f"\nEtot({ha2kelvin(cell.occ.smearing):.2f} K) = {scf.energies.Etot:.6f} Eh")
   print(f"Etot({0:>7.2f} K) = {scf.energies.extrapolate():.6f} Eh")
   

Calculate the Fermi energy

.. code-block:: python

   print(f"\nEf = {get_Efermi(scf):.6f} Eh")

Download :download:`20_smeared_occupations.py <../../examples/20_smeared_occupations/20_smeared_occupations.py>`