.. _basic:

Basic functions in mcu 
======================

You can use the code by either writing a simple python script.

.. code-block:: bash

    $ python mymcu.py
    
or work interactively in python environment (I prefer this way):

.. code-block:: bash

    $ python 

**Compute bandgap and Fermi level:**

**mcu.VASP** works with vasprun.xml and OUTCAR (optional). 
OUTCAR is only used in case Fermi level cannot be read from vasprun.xml

.. code-block:: python
   :linenos:
   
   import mcu
   mymcu = mcu.VASP()    # Define an mcu object
   mymcu.get_bandgap()   # Get the bandgap
   mymcu.efermi          # Get Fermi level                         

**WAVEDER and WAVEDERF file can be read from mcu**

.. code-block:: python
   :linenos:
   
   import mcu
   cder, nodesn_i_dielectric_function, wplasmon = mcu.read_WAVEDER(waveder = 'WAVEDER')
   cder = mcu.read_WAVEDERF(wavederf = 'WAVEDERF')

**Generate k-mesh list from a k-path**

Providing a high symmetric k-point coordinates and labels (can be get from `BCS <http://www.cryst.ehu.es/cryst/get_kvec.html>`_), 
**mcu** can generate KPOINTS file following a k-path. This k-mesh is used to compute band structure in the unconventional way (e.g. hydrib functional). 
You need to copy the k-mesh (for SCF) from IBZKPT file to the KPOINTS file generated by **mcu**.

.. code-block:: python
   :linenos:
   
   import mcu
   kpath ='''
   Y 0.5 0.0 0.0
   G 0.0 0.0 0.0
   X 0.0 0.5 0.0
   R 0.5 0.5 0.0
   Y-G-R-X-G
   '''
   kmesh = mcu.make_KPOINTS(kpath, npoint=10)