mirror of https://github.com/triqs/dft_tools
123 lines
6.1 KiB
ReStructuredText
123 lines
6.1 KiB
ReStructuredText
.. _analysis:
|
|
|
|
Tools for analysis
|
|
==================
|
|
|
|
.. warning::
|
|
TO BE UPDATED!
|
|
|
|
This section explains how to use some tools of the package in order to analyse the data.
|
|
|
|
.. warning::
|
|
The package does NOT provide an explicit method to do an **analytic continuation** of the
|
|
self energies and Green functions from Matsubara frequencies to the real frequancy axis!
|
|
There are methods included e.g. in the :program:`ALPS` package, which can be used for these purposes. But
|
|
be careful: All these methods have to be used very carefully!
|
|
|
|
The tools for analysis can be found in an extension of the :class:`SumkDFT` class and are
|
|
loaded by importing the module :class:`SumkDFTTools`::
|
|
|
|
from pytriqs.applications.dft.sumk_dft_tools import *
|
|
|
|
There are two practical tools for which you do not need a self energy on the real axis, namely the:
|
|
|
|
* density of states of the Wannier orbitals,
|
|
* partial charges according to the Wien2k definition.
|
|
|
|
The self energy on the real frequency axis is necessary in computing the:
|
|
|
|
* momentum-integrated spectral function including self-energy effects,
|
|
* momentum-resolved spectral function (i.e. ARPES).
|
|
|
|
The initialisation of the class is equivalent to that of the :class:`SumkDFT`
|
|
class::
|
|
|
|
SK = SumkDFTTools(hdf_file = filename)
|
|
|
|
Note that all routines available in :class:`SumkDFT` are also available here.
|
|
|
|
Routines without real-frequency self energy
|
|
-------------------------------------------
|
|
|
|
For plotting the
|
|
density of states of the Wannier orbitals, you simply type::
|
|
|
|
SK.check_input_dos(om_min, om_max, n_om)
|
|
|
|
which produces plots between the real frequencies `om_min` and `om_max`, using a mesh of `n_om` points. There
|
|
is an optional parameter `broadening` which defines an additional Lorentzian broadening, and has the default value of
|
|
`0.01` by default.
|
|
|
|
Since we can calculate the partial charges directly from the Matsubara Green's functions, we also do not need a
|
|
real-frequency self energy for this purpose. The calculation is done by::
|
|
|
|
ar = HDFArchive(SK.hdf_file)
|
|
SK.put_Sigma([ ar['SigmaImFreq'] ])
|
|
del ar
|
|
dm = SK.partial_charges()
|
|
|
|
which calculates the partial charges using the data stored in the hdf5 file, namely the self energy, double counting, and
|
|
chemical potential. Here we assumed that the final self energy is stored as `SigmaImFreq` in the archive.
|
|
On return, `dm` is a list, where the list items correspond to the density matrices of all shells
|
|
defined in the list `SK.shells`. This list is constructed by the Wien2k converter routines and stored automatically
|
|
in the hdf5 archive. For the detailed structure of `dm`, see the reference manual.
|
|
|
|
|
|
Routines with real-frequency self energy
|
|
----------------------------------------
|
|
|
|
In order to plot data including correlation effects on the real axis, one has to provide the real frequency self energy.
|
|
Most conveniently, it is stored as a real frequency :class:`BlockGf` object in the hdf5 file::
|
|
|
|
ar = HDFArchive(filename+'.h5','a')
|
|
ar['SigmaReFreq'] = SigmaReFreq
|
|
del ar
|
|
|
|
You may also store it in text files. If all blocks of your self energy are of dimension 1x1, you store them in `fname_(block)0.dat` files. Here `(block)` is a block name (`up`, `down`, or combined `ud`). In the case when you have matrix blocks, you store them in `(i)_(j).dat` files, where `(i)` and `(j)` are the orbital indices, in the `fname_(block)` directory.
|
|
|
|
This self energy is loaded and put into the :class:`SumkDFT` class by the function::
|
|
|
|
SK.constr_Sigma_real_axis(filename, hdf=True, hdf_dataset='SigmaReFreq',n_om=0)
|
|
|
|
where:
|
|
|
|
* `filename`: the name of the hdf5 archive file or the `fname` pattern in text files names as described above,
|
|
* `hdf`: if `True`, the real-axis self energy will be read from the hdf5 file, otherwise from the text files,
|
|
* `hdf_dataset`: the name of dataset where the self energy is stored in the hdf5 file,
|
|
* `n_om`: the number of points in the real-axis mesh (used only if `hdf=False`).
|
|
|
|
The chemical potential as well as the double counting correction were already read in the initialisation process.
|
|
|
|
With this self energy, we can now execute::
|
|
|
|
SK.dos_partial(broadening=broadening)
|
|
|
|
This produces both the momentum-integrated (total density of states or DOS) and orbitally-resolved (partial/projected DOS) spectral functions.
|
|
The variable `broadening` is an additional Lorentzian broadening applied to the resulting spectra.
|
|
The output is printed into the files
|
|
|
|
* `DOScorr(sp).dat`: The total DOS, where `(sp)` stands for `up`, `down`, or combined `ud`. The latter case
|
|
is relevant for calculations including spin-orbit interaction.
|
|
* `DOScorr(sp)_proj(i).dat`: The DOS projected to an orbital with index `(i)`. The index `(i)` refers to
|
|
the indices given in ``SK.shells``.
|
|
* `DOScorr(sp)_proj(i)_(m)_(n).dat`: As above, but printed as orbitally-resolved matrix in indices
|
|
`(m)` and `(n)`. For `d` orbitals, it gives the DOS seperately for, e.g., :math:`d_{xy}`, :math:`d_{x^2-y^2}`, and so on.
|
|
|
|
Another quantity of interest is the momentum-resolved spectral function, which can directly be compared to ARPES
|
|
experiments. We assume here that we already converted the output of the :program:`dmftproj` program with the
|
|
converter routines (see :ref:`interfacetowien`). The spectral function is calculated by::
|
|
|
|
SK.spaghettis(broadening)
|
|
|
|
Optional parameters are
|
|
|
|
* `shift`: An additional shift added as `(ik-1)*shift`, where `ik` is the index of the `k` point. This is useful for plotting purposes.
|
|
The default value is 0.0.
|
|
* `plotrange`: A list with two entries, :math:`\omega_{min}` and :math:`\omega_{max}`, which set the plot
|
|
range for the output. The default value is `None`, in which case the full momentum range as given in the self energy is used.
|
|
* `ishell`: An integer denoting the orbital index `ishell` onto which the spectral function is projected. The resulting function is saved in
|
|
the files. The default value is `None`. Note for experts: The spectra are not rotated to the local coordinate system used in :program:`Wien2k`.
|
|
|
|
The output is written as the 3-column files ``Akw(sp).dat``, where `(sp)` is defined as above. The output format is
|
|
`k`, :math:`\omega`, `value`.
|