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Added preliminary parser description to the docs

This is a description of the preliminary design for the parser of
PROJCAR/LOCPROJ files output by VASP.
This commit is contained in:
Oleg E. Peil 2015-10-13 14:08:10 +02:00
parent 8064c9604d
commit aa39c37d8b

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VASP input-output
#################
The following VASP are used by PLOtools:
* PLOCAR: raw projectors generated by VASP-PLO interface
* EIGENVAL: Kohn-Sham eigenvalues as well as `k`-points with weights
The following VASP files are used by PLOtools:
* PROJCAR, LOCPROJ: raw projectors generated by VASP-PLO interface (VASP version >= 5.4.1)
* EIGENVAL: Kohn-Sham eigenvalues as well as `k`-points with weights and Fermi weights
* IBZKPT: `k`-point data (:math:`\Gamma`)
* POSCAR: crystal structure data
Starting from version 5.4.1 VASP now supports an official output of various types of
projectors that are requested in INCAR by specifying a set of sites, orbitals and types
of projectors. The calculated projectors are output into files **PROJCAR** and **LOCPROJ**.
The difference between these two files is that **LOCPROJ** contains raw matrices without
any reference to sites/orbitals, while **PROJCAR** is more detailed on that.
In particular, the information that can be obtained for each projector from **PROJCAR** is the following:
* site (and species) index
* for each `k`-point and band: a set of complex numbers for labeled orbitals
At the same time, **LOCPROJ** contains the total number of projectors (as well as the
number of `k`-points, bands, and spin channels) in the first line,
which can be used to allocate the arrays before parsing.
To enhance the performance of the parser, it is implemented in plain C. The idea is
that the python part of the parser first reads the first line of **LOCPROJ** and
then calls the C-routine with necessary parameters to parse **PROJCAR**.