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118 lines
5.5 KiB
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118 lines
5.5 KiB
ReStructuredText
.. _analysis:
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Analysing tools
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===============
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This section explains how to use some tools of the package in order to analyse the data.
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.. warning::
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The package does NOT provide an explicit method to do an analytic continuation of the
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self energies and Green functions from Matsubara frequencies to the real frequancy axis!
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There are methods included e.g. in the ALPS package, which can be used for these purposes. But
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be careful: All these methods have to be used very carefully!!
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The analysing tools can be found in an extension of the :class:`SumkLDA` class, they are
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loaded by::
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from pytriqs.applications.dft.sumk_lda_tools import *
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This import the module ``SumkLDATools``. There are two practical tools, for which you don't
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need a self energy on the real axis:
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* The density of states of the Wannier orbitals.
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* Partial charges according to the Wien2k definition.
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Other routines need the self energy on the real frequency axis. If you managed to get them, you can
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calculate
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* the momentum-integrated spectral function including self-energy effects.
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* the momentum-resolved spectral function (i.e. ARPES)
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The initialisation of the class is completely equivalent to the initialisation of the :class:`SumkLDA`
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class::
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SK = SumkLDATools(hdf_file = filename)
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By the way, all routines available in :class:`SumkLDA` are also available here.
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Routines without real-frequency self energy
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-------------------------------------------
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For plotting the
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density of states of the Wannier orbitals, you simply type::
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SK.check_input_dos(om_min, om_max, n_om)
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which produces plots between real frequencies `ommin` and `ommax`, using a mesh of `N_om` points. There
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is an optional parameter, `broadening`, which defines an additional Lorentzian broadening, and is set to `0.01`
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by default.
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Since we can calculate the partial charges directly from the Matsubara Green's functions, we also don't need a
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real frequency self energy for this purpose. The calculation is done by::
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ar = HDFArchive(SK.hdf_file)
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SK.put_Sigma([ ar['SigmaF'] ])
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del ar
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dm = SK.partial_charges()
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which calculates the partial charges using the input that is stored in the hdf5 file (self energy, double counting,
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chemical potential). Here we assumed that the final self energy is stored as `SigmaF` in the archive.
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On return, dm is a list, where the list items correspond to the density matrices of all shells
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defined in the list ``SK.shells``. This list is constructed by the Wien2k converter routines and stored automatically
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in the hdf5 archive. For the detailed structure of `dm`, see the reference manual.
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Routines with real-frequency self energy
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----------------------------------------
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In order to plot data including correlation effects on the real axis, one has to provide the real frequency self energy.
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Most conveniently, it is stored as a real frequency :class:`BlockGf` object in the hdf5 file. There is one important thing to
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keep in mind. The real frequency self energy has to carry the note `ReFreq`::
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SigmaReFreq.note = 'ReFreq'
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This tells the SumkLDA routines, that it is indeed a real frequency Greens function. Supposed you have your self energy now
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in the archive, you can type::
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ar=HDFArchive(SK.hdf_file)
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SK.put_Sigma([ ar['SigmaReFreq'] ])
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del ar
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This loads the self energy and puts it into the :class:`SumkLDA` class. The chemical potential as well as the double
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counting correction was already read in the initialisation process.
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With this self energy, we can do now::
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SK.dos_partial()
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This produces the momentum-integrated spectral functions (density of states, DOS), also orbitally resolved.
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The output is printed into the files
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* `DOScorr(sp).dat`: The total DOS. `(sp)` stands for `up`, `down`, or combined `ud`. The latter case
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is relevant for calculations including spin-orbit interaction.
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* `DOScorr(sp)_proj(i).dat`: The DOS projected to an orbital with index `(i)`. The index `(i)` refers to
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the indices given in ``SK.shells``.
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* `DOScorr(sp)_proj(i)_(m)_(n).dat`: Sames as above, but printed as orbitally resolved matrix in indices
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`(m)` and `(n)`. For `d` orbitals, it gives separately the DOS
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for, e.g., :math:`d_{xy}`, :math:`d_{x^2-y^2}`, and so on.
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Another quantity of interest is the momentum-resolved spectral function, which can directly be compared to ARPES
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experiments. We assume here that we already converted the output of the :program:`dmftproj` program with the
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converter routines, see :ref:`interfacetowien`. The spectral function is calculated by::
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SK.spaghettis(broadening)
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The variable `broadening`1 is an additional Lorentzian broadening that is added to the resulting spectra. The output is
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written as the 3-column files ``Akw(sp).dat``, where `(sp)` has the same meaning as above. The output format is
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`k`, :math:`\omega`, `value`. Optional parameters are
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* `shift`: An additional shift, added as `(ik-1)*shift`, where `ik` is the index of the `k` point. Useful for plotting purposes,
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standard value is 0.0.
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* `plotrange`: A python list with two entries, first being :math:`\omega_{min}`, the second :math:`\omega_{max}`, setting the plot
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range for the output. Standard value is `None`, in this case the momentum range as given in the self energy is plotted.
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* `ishell`: If this is not `None` (standard value), but an integer, the spectral function projected to the orbital with index `ishell`
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is plotted to the files. Attention: The spectra are not rotated to the local coordinate system as used in the :program:`Wien2k`
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program (For experts).
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