7.1. st2abics

It is sometimes quite tedious to prepare the [config] section in abICS input files. To facilitate this, we provide the st2abics tool, which takes a structure file readable by pymatgen and converts it to an abICS input template with the [config] section filled in. An additional control file is required to tell st2abics how to break down the original structure file into config.base_structure and config.defect_structure (see [config] section for definitions). The tool is used as follows:

$ st2abics -h
usage: st2abics [-h] inputfi structurefi [outfi]

Prepare abICS config from structure file

positional arguments:
  inputfi      toml input file for st2abics
  structurefi  Structure file that can be read by pymatgen Structure.from_file() method
  outfi        Output file to be used as abics input. Defaults to standard output

optional arguments:
  -h, --help   show this help message and exit

Examples are provided in examples/st2abics and can be run as follows:

$ cd examples/st2abics
$ st2abics st2abics_MgAl2O4.toml MgAl2O4.vasp abics_MgAl2O4.toml # spinel
$ st2abics st2abics_CuZn.toml CuZn.vasp abics_CuZn.toml # brass
$ st2abics st2abics_BZY.toml BaZrO3.vasp abics_BZY.toml # Y-doped BaZrO3

The resulting files (abics_MgAl2O4.toml, abics_CuZn.toml, and abics_BZY.toml in the above example) can be used as abICS input after filling in the [mlref], [train], [sampling] and [observer] sections.

7.1.1. Input Format

Examples of st2abics input files can be found in examples/st2abics (st2abics_CuZn.toml, st2abics_MgAl2O4.toml, and st2abics_BZY.toml in the above example).

The format is similar to [config] section of abICS input file.

7.1.2. Keywords

• supercell

  Format : list

  Description : The size of supercell by the list format [ \(\bf{a}, \bf{b}, \bf{c}\) ].

• [[config.base_structure]] section

  This section specifies how to construct the base_structure that does not exchange atoms between lattice sites during the Monte Carlo calculation.

  • species

    Format : list of str

    Description : Atomic species of the base_structure. The corresponding coordinates are extracted automatically from the input structure file.

  • fix

    Format : bool

    Description : Whether to disallow local relaxation of the base_structure (true) or not (false).

• [[config.defect_structure]] section(s)

  This section specifies the sublattice for configurational sampling. There can be more than one [[config.defect_structure]] section, e.g., one for cations and one for anions.

  • site_center_species

    Format : list of str

    Description : The species in the original structure file whose coordinates are used as lattice sites for configurational sampling.

  • [[config.defect_structure.groups]] subsection(s) This section specifies the atom groups that reside on the lattice sites for configurational sampling. If not provided, it will be constructed automatically from the original structure file using site_center_species.

    • name

      Format : str

      Description : The name of atom group.

    • species

      Format : list of str

      Description : The atom species belonging to the atom group. The default value is a list containing only one species specified by name. Elements that do not appear in the original structure file can also be specified. A vacancy can be represented by an empty list []. As an example, see st2abics_BZY.toml in the example directory.

    • coords

      Format : list of lists of lists or str

      Description : The coordinates of each atom in the atom group for each orientation that the atom group can take (see description for coords here). Default value is [[[0.0, 0.0, 0.0]]].

    • num

      Format : int

      Description : The number of atom groups of the type specified in this section. Make sure to specify the number based on the sites in the supercell, which may be larger than the original structure file read in by st2abics.