mirror of https://github.com/triqs/dft_tools
168 lines
7.4 KiB
ReStructuredText
168 lines
7.4 KiB
ReStructuredText
.. _plovasp:
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PLOVasp
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=======
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The general purpose of the PLOVasp tool is to transform raw, non-normalized
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projectors generated by VASP into normalized projectors corresponding to
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user-defined projected localized orbitals (PLO). The PLOs can then be used for
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DFT+DMFT calculations with or without charge self-consistency. PLOVasp also
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provides some utilities for basic analysis of the generated projectors, such as
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outputting density matrices, local Hamiltonians, and projected density of
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states.
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PLOs are determined by the energy window in which the raw projectors are
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normalized. This allows to define either atomic-like strongly localized Wannier
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functions (large energy window) or extended Wannier functions focusing on
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selected low-energy states (small energy window).
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In PLOVasp, all projectors sharing the same energy window are combined into a
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`projector group`. Technically, this allows one to define several groups with
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different energy windows for the same set of raw projectors. Note, however,
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that DFTtools does not support projector groups at the moment but this feature
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might appear in future releases.
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A set of projectors defined on sites related to each other either by symmetry
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or by an atomic sort, along with a set of :math:`l`, :math:`m` quantum numbers,
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forms a `projector shell`. There could be several projectors shells in a
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projector group, implying that they will be normalized within the same energy
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window.
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Projector shells and groups are specified by a user-defined input file whose
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format is described below.
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Input file format
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-----------------
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The input file is written in the standard config-file format.
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Parameters (or 'options') are grouped into sections specified as
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`[Section name]`. All parameters must be defined inside some section.
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A PLOVasp input file can contain three types of sections:
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#. **[General]**: includes parameters that are independent
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of a particular projector set, such as the Fermi level, additional
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output (e.g. the density of states), etc.
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#. **[Group <Ng>]**: describes projector groups, i.e. a set of
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projectors sharing the same energy window and normalization type.
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At the moment, DFTtools support only one projector group, therefore
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there should be no more than one projector group.
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#. **[Shell <Ns>]**: contains parameters of a projector shell labelled
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with `<Ns>`. If there is only one group section and one shell section,
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the group section can be omitted but in this case, the group required
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parameters must be provided inside the shell section.
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Section [General]
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"""""""""""""""""
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The entire section is optional and it contains three parameters:
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* **BASENAME** (string): provides a base name for output files.
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Default filenames are :file:`vasp.*`.
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* **DOSMESH** ([float float] integer): if this parameter is given,
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the projected density of states for each projected orbital will be
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evaluated and stored to files :file:`pdos_<n>.dat`, where `n` is the
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orbital index. The energy
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mesh is defined by three numbers: `EMIN` `EMAX` `NPOINTS`. The first two
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can be omitted in which case they are taken to be equal to the projector
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energy window. **Important note**: at the moment this option works
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only if the tetrahedron integration method (`ISMEAR = -4` or `-5`)
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is used in VASP to produce `LOCPROJ`.
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* **EFERMI** (float): provides the Fermi level. This value overrides
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the one extracted from VASP output files.
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There are no required parameters in this section.
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Section [Shell]
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"""""""""""""""
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This section specifies a projector shell. Each `[Shell]` section must be
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labeled by an index, e.g. `[Shell 1]`. These indices can then be referenced
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in a `[Group]` section.
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In each `[Shell]` section two parameters are required:
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* **IONS** (list of integer): indices of sites included in the shell.
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The sites can be given either by a list of integers `IONS = 5 6 7 8`
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or by a range `IONS = 5..8`. The site indices must be compatible with
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the POSCAR file.
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* **LSHELL** (integer): :math:`l` quantum number of the desired local states.
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It is important that a given combination of site indices and local states
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given by `LSHELL` must be present in the LOCPROJ file.
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There are additional optional parameters that allow one to transform
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the local states:
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* **TRANSFORM** (matrix): local transformation matrix applied to all states
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in the projector shell. The matrix is defined by a (multiline) block
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of floats, with each line corresponding to a row. The number of columns
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must be equal to :math:`2 l + 1`, with :math:`l` given by `LSHELL`. Only real matrices
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are allowed. This parameter can be useful to select certain subset of
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orbitals or perform a simple global rotation.
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* **TRANSFILE** (string): name of the file containing transformation
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matrices for each site. This option allows for a full-fledged functionality
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when it comes to local state transformations. The format of this file
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is described :ref:`below <transformation_file>`.
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Section [Group]
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"""""""""""""""
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Each defined projector shell must be part of a projector group. In the current
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implementation of DFTtools only a single group (labelled by any integer, e.g. `[Group 1]`)
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is supported. This implies that all projector shells
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must be included in this group.
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Required parameters for any group are the following:
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* **SHELLS** (list of integers): indices of projector shells included in the group.
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All defined shells must be grouped.
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* **EWINDOW** (float float): the energy window specified by two floats: bottom
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and top. All projectors in the current group are going to be normalized within
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this window. *Note*: This option must be specified inside the `[Shell]` section
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if only one shell is defined and the `[Group]` section is omitted.
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Optional group parameters:
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* **NORMALIZE** (True/False): specifies whether projectors in the group are
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to be normalized. The default value is **True**.
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* **NORMION** (True/False): specifies whether projectors are normalized on
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a per-site (per-ion) basis. That is, if `NORMION = True`, the orthogonality
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condition will be enforced on each site separately but the Wannier functions
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on different sites will not be orthogonal. If `NORMION = False`, the Wannier functions
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on different sites included in the group will be orthogonal to each other.
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.. _transformation_file:
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File of transformation matrices
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"""""""""""""""""""""""""""""""
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.. warning::
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The description below applies only to collinear cases (i.e., without spin-orbit
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coupling). In this case, the matrices are spin-independent.
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The file specified by option `TRANSFILE` contains transformation matrices
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for each ion. Each line must contain a series of floats whose number is either equal to
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the number of orbitals :math:`N_{orb}` (in this case the transformation matrices
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are assumed to be real) or to :math:`2 N_{orb}` (for the complex transformation matrices).
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The total number of lines :math:`N` must be a multiple of the number of ions :math:`N_{ion}`
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and the ratio :math:`N / N_{ion}`, then, gives the dimension of the transformed
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orbital space. The lines with floats can be separated by any number of empty or
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comment lines (starting from `#`), which are ignored.
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A very simple example is a transformation matrix that selects the :math:`t_{2g}` manifold.
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For two correlated sites, one can define the file as follows:
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::
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# Site 1
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1.0 0.0 0.0 0.0 0.0
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0.0 1.0 0.0 0.0 0.0
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0.0 0.0 0.0 1.0 0.0
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# Site 2
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1.0 0.0 0.0 0.0 0.0
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0.0 1.0 0.0 0.0 0.0
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0.0 0.0 0.0 1.0 0.0
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