httk.io.vasp.poscar_reader

A string-preserving reader for VASP POSCAR/CONTCAR files.

read_poscar() parses a POSCAR/CONTCAR file into a neutral, JSON-able mapping whose numeric fields are kept as the verbatim strings found in the file. It performs no numeric conversion and imports nothing from httk-atomistic; turning the mapping into a Structure is the job of httk.atomistic.structure_from_poscar.

Functions

read_poscar(→ dict[str, Any])

Parse a VASP POSCAR/CONTCAR into a neutral, string-preserving mapping.

Module Contents

httk.io.vasp.poscar_reader.read_poscar(source: Any) → dict[str, Any]

Parse a VASP POSCAR/CONTCAR into a neutral, string-preserving mapping.

source may be a filename (str or os.PathLike, opened through httk.core.TextstreamFileView so compressed files such as CONTCAR.bz2 are decompressed transparently) or an already-open text stream / iterable of lines.

The returned mapping has the keys format (always "vasp-poscar"), comment, scale and volume (exactly one is a string, the other None), cell (a 3x3 list of coordinate strings), symbols (list[str] for VASP-5, None for VASP-4), counts (list[int]), cartesian (bool), coords (an N``x3 list of strings), and ``selective_dynamics (an N``x3 list of booleans when the file declares selective dynamics, else ``None). Malformed input raises a clear ValueError naming the offending line.

Three further keys report how precisely the file wrote its numbers, each the coarsest claim among the tokens it covers, or None when none of them claim anything: cell_precision, scale_precision, and coordinate_precision. They are the precisions of the tokens as written, deliberately not converted: the cell vectors are still to be multiplied by the scaling factor, and the coordinates may be Cartesian or fractional depending on cartesian. Doing that conversion needs the assembled cell, so it belongs to whoever builds the structure — httk.atomistic.structure_from_poscar() — not to the reader.