httk.atomistic.vasp_structures

Build an exact Structure from a neutral POSCAR mapping.

structure_from_poscar() consumes the plain, string-preserving mapping produced by httk.io.read_poscar (format tag "vasp-poscar") and turns it into an exact Structure. It imports nothing from httk-io — it only understands the neutral mapping shape — keeping the parsing capability (httk-io) and the domain model (httk-atomistic) decoupled.

load_structure() is the convenience end-to-end entry point: httk.core.load picks the reader by file type, and a small adapter table maps the payload’s "format" tag to the matching structure builder.

Functions

structure_from_poscar(→ httk.atomistic.structure.Structure)	Build an exact Structure from a neutral POSCAR mapping.
load_structure(→ httk.atomistic.structure.Structure)	Load a file and build a Structure from it.

Module Contents

httk.atomistic.vasp_structures.structure_from_poscar(data: collections.abc.Mapping[str, Any]) → httk.atomistic.structure.Structure

Build an exact Structure from a neutral POSCAR mapping.

data is the mapping returned by httk.io.read_poscar (its format must be "vasp-poscar"). The cell basis is taken exactly from the file’s string rows. For a positive universal scaling factor the scale string is used directly as the cell’s exact scale; for a negative scaling factor (a target volume V) the scale is the cube root of V / |det(basis)| — a value outside the exact surd field, so it is a deterministic rational approximation (the basis rows themselves stay exact).

Direct coordinates become reduced coordinates directly (exact strings). Cartesian coordinates are converted exactly as cart * basis.inv() under the row-vector convention; because VASP scales both the lattice vectors and the Cartesian positions by the universal scaling factor, that factor cancels and the reduced coordinates are exact regardless of the scale/volume case.

Species come from the VASP-5 species line (one single-element, unattached Species of concentration 1.0 per distinct symbol); a VASP-4 file (no species symbols) raises a ValueError. Selective dynamics flags, if present, are ignored.

httk.atomistic.vasp_structures.load_structure(path: str) → httk.atomistic.structure.Structure

Load a file and build a Structure from it.

httk.core.load(path) selects the reader by file type (transparently decompressing .bz2 / .gz files); the payload’s "format" tag then selects the matching structure builder. A payload without a recognized "format" tag (for example a CIF, which returns a different shape) raises a clear ValueError.