wrote the structure part

doc/basicnotions/structure.rst

@@ -1,11 +1,112 @@
 Structure of DFT Tools
 ======================
 
-.. warning::
-   TO BE WRITTEN!
-
 .. image:: images/structure.png
    :width: 700
    :align: center
 
+The central part of :program:`dft_tools`, which is performing the
+steps for the DMFT self-consistency cycle, is written following the
+same philosophy as the :ref:`TRIQS <triqslibs:welcome>` toolbox. At
+the user level, easy-to-use python modules are provided that allow to
+write simple and short scripts performing the actual
+calculation. Here, we will describe the general structure of the
+package, for the details of how to use the modules, please consult the 
+user guide of this :ref:`documentation`.
+
+The interface layer
+-------------------
+
+Since the input for this DMFT part has to be provided by DMFT
+calculations, there needs to be another layer that connects the
+python-based modules with the DFT output. Naturally, this layer
+depends on the DFT package at hand. At the moment, there is an
+interface to the Wien2k band structure package, and a very light 
+interface that can be used in a more general setup. Note that this
+light interface layer **dows not** allow full charge self-consistent
+calculations. 
+
+Wien2k interface
+""""""""""""""""
+
+This interface layer consists of two parts. First, the output from Wien2k
+is taken, and localised Wannier orbitals are constructed. This is done
+by the fortran program :program:`dmftproj`. The second part consist in
+the conversion of the :program:`dmftproj` into the hdf5 file
+format to be used for the DMFT calculation. This step is done by a
+python routine called :class:`Wien2kConverter`, that reads the text output and
+creates the hdf5 input file with the necessary ingredients. Quite
+naturally, :program:`dft_tools` will adopt this converter concept also for future
+developments for other DFT packages.
+
+General interface
+"""""""""""""""""
+
+In addition to the specialised Wien2k interface, :program:`dft_tools`
+provides also a very light-weight general interface. It basically
+consists of a very simple :class:`HkConverter`. As input it requires a
+hamiltonian matrix :math:`H_{mn}(\mathbf{k})` written already in
+localised-orbital indices :math:`m,n`, on a :math:`\mathbf{k}`-point
+grid covering the Brillouin zone, and just a few other informations
+like total numer of electrons, how many correlated atoms in the unit
+cell, and so on. It converts this hamiltonian into a hdf5 format and 
+sets some variables to standard values, such that it can be used with
+the python modules performing the DMFT calculation. How the
+hamiltonian matrix :math:`H_{mn}(\mathbf{k})` is actually calculated,
+is **not** part of this interace.
+
+The DMFT calculation
+--------------------
+
+As mentioned above, there are a few python routines that allow to
+perform the multi-band DMFT calculation in the context of real
+materials. The major part is contained inte module
+:class:`SumkDFT`. It contains routines to
+       
+* calculate local Greens functions
+* do the upfolding and downfolding from Bloch bands to Wannier
+  orbitals
+* calculate the double-counting correction
+* calculate the chemical potential in order to get the electron count right    
+* other things like determining the structure of the local
+  hamiltonian, rotating from local to global coordinate systems, etc.
+
+At the user level, all these routines can be used to construct
+situation- and problem-dependent DMFT calculations in a very efficient
+way.
+
+Full charge self consistency
+----------------------------
+
+Using the Wien2k interface, one can perform full charge
+self-consistent calculations. :class:`SumkDFT` provides routines to
+calculate the correlated density matrix and stores it in a format that
+can be read in by the :program:`lapw2` part of the Wien2k
+package. Changing a one-shot calculation in a full charge
+self-consistent one is only a couple of additional lines in the code! 
+
+Post-processing
+---------------
+
+The main result of DMFT calculation is the interacting Greens function
+and the Self energy. However, one is normally interested in
+quantitites like band structure, density of states, or transport
+properties. In order to calculate these things, :program:`dft_tools`
+provides the post-processing modules :class:`SumkDFTTools`. It
+contains routines to calculate
+
+* (projected) density of states
+* partial charges
+* correlated band structures (*spaghettis*)
+* transport properties such as optical conductivity, resistivity,
+  or thermopower.
+
+.. warning::
+   At the moment neither :ref:`TRIQS<triqslibs:welcome>` nor :program:`dft_tools`
+   provides Maximum Entropy routines! You can use the Pade
+   approximants implemented in the TRIQS library, or you use your own
+   home-made Maximum Entropy code to do the analytic continuation from
+   Matsubara to the real-frequency axis.
+
+   
 

doc/index.rst

@@ -13,7 +13,7 @@ correlated materials, combining realistic DFT band-structure
 calculations with the dynamical mean-field theory. Together with the
 necessary tools to perform the DMFT self-consistency loop for
 realistic multi-band problems, the package provides a full-fledged
-charge self-consistent interface to the `WIEN2K package
+charge self-consistent interface to the `Wien2K package
 <http://www.wien2k.at>`_. In addition, if Wien2k is not available, it
 provides a generic interface for one-shot DFT+DMFT calculations, where
 only the single-particle Hamiltonian in orbital space has to be