mirror of
https://github.com/triqs/dft_tools
synced 2024-08-16 09:18:28 +02:00
75 lines
4.5 KiB
ReStructuredText
75 lines
4.5 KiB
ReStructuredText
.. _nio_csc:
|
|
|
|
DFT and projections
|
|
==================================================
|
|
|
|
We will perform charge self-consitent DFT+DMFT calcluations for the charge-transfer insulator NiO. We start from scratch and provide all necessary input files to do the calculations: First for doing a single-shot calculation and then for charge-selfconsistency.
|
|
|
|
VASP setup
|
|
-------------------------------
|
|
We start by running a simple VASP calculation to converge the charge density initially.
|
|
Use the :ref:`INCAR`, :ref:`POSCAR`, and :ref:`KPOINTS` provided and use your
|
|
own :file:`POTCAR` file.
|
|
|
|
Let us take a look in the :file:`INCAR`, where we have to specify local orbitals as basis
|
|
for our many-body calculation.
|
|
|
|
.. literalinclude:: images_scripts/INCAR
|
|
|
|
`LORBIT = 14` takes care of optimizing the projectors in the energy window defined
|
|
by `EMIN` and `EMAX`. We switch off all symmetries with `ISYM=-1` since symmetries
|
|
are not implemented in the later DMFT scripts. Finally, we select the relevant orbitals
|
|
for atom 1 (Ni, d-orbitals) and 2 (O, p-orbitals) by the two `LOCPROJ` lines.
|
|
For details refer to the VASP wiki on the `LOCPROJ <https://cms.mpi.univi
|
|
e.ac.at/wiki/index.php/LOCPROJ>`_ flag. The projectors are stored in the file `LOCPROJ`.
|
|
|
|
|
|
plovasp
|
|
------------------------------
|
|
Next, we postprocess the projectors, which VASP stored in the file `LOCPROJ`.
|
|
We do this by invoking :program:`plovasp plo.cfg` which is configured by an input file, e.g., named :ref:`plo.cfg`.
|
|
|
|
.. literalinclude:: images_scripts/plo.cfg
|
|
|
|
Here, in `[General]` we set the basename and the grid for calculating the density of
|
|
states. In `[Group 1]` we define a group of two shells which are orthonormalized with
|
|
respect to states in an energy window from `-9` to `2` for all ions simultanously
|
|
(`NORMION = False`). We define the two shells, which correspond to the Ni d states
|
|
and the O p states. Only the Ni shell is treated as correlated (`CORR = True`), i.e.,
|
|
is supplemented with a Coulomb interaction later in the DMFT calculation.
|
|
|
|
Converting to hdf5 file
|
|
-------------------------------
|
|
We gather the output generated by :program:`plovasp` into a hdf5 archive which :program:`dft_tools` is able to read. We do this by running :program:`python converter.py` on the script :ref:`converter.py`:
|
|
|
|
.. literalinclude:: images_scripts/converter.py
|
|
|
|
Now we are all set to perform a dmft calculation.
|
|
|
|
DMFT
|
|
==================================================
|
|
|
|
dmft script
|
|
------------------------------
|
|
|
|
Since the python script for performing the dmft loop pretty much resembles that presented in the tutorial on :ref:`srvo3`, we will not go into detail here but simply provide the script :ref:`nio.py`. Following Kunes et al. in `PRB 75 165115 (2007) <https://journals.aps.org/prb/abstract/10.1103/PhysRevB.75.165115>`_ we use :math:`U=8` and :math:`J=1`. We se;ect :math:`\beta=5` instead of :math:`\beta=10` to ease the problem slightly. For simplicity we fix the double-counting potential to :math:`\mu_{DC}=59` eV by::
|
|
|
|
DC_value = 59.0
|
|
SK.calc_dc(dm, U_interact=U, J_hund=J, orb=0, use_dc_value=DC_value)
|
|
|
|
For sensible results run this script in parallel on at least 20 cores. As a quick check of the results, we can compare the orbital occupation from the paper cited above (:math:`n_{eg} = 0.54` and :math:`n_{t2g}=1.0`) and those from the cthyb output (check lines `Orbital up_0 density:` for a t2g and `Orbital up_2 density:` for an eg orbital). They should coincide well.
|
|
|
|
|
|
Local lattice Green's function for all projected orbitals
|
|
----------------------
|
|
We calculate the local lattice Green's function - now also for the uncorrelated orbitals, i.e., the O p states, for what we use the script :ref:`NiO_local_lattice_GF.py`. The result is saved in the h5 file as `G_latt_orb_it<n_it>`, where `n_it>` is the number of the last DMFT iteration.
|
|
|
|
Spectral function on real axis: MaxEnt
|
|
----------------------
|
|
To compare to results from literature we make use of the `maxent triqs application <https://triqs.github.io/maxent/master/>`_ and calculate the spectral function on real axis. Use this script to perform a crude but quick calculation: :ref:`maxent.py` using a linear real axis and a line-fit analyzer to determine the optimal :math:`\alpha`. The output is saved in the h5 file in `DMFT_results/Iterations/G_latt_orb_w_o<n_o>_it<n_it>`, where `<n_o>` is the number of the orbital and `n_it` is again the number of the last iteration. The real axis information is stored in `DMFT_results/Iterations/w_it<n_it>`.
|
|
|
|
|
|
.. image:: images_scripts/nio_Aw.png
|
|
:width: 400
|
|
:align: center
|