1. Load and inspect a structure

With httk-atomistic installed, httk.core.load() provides a one-call atomistic loading experience through a format adapter registered during registry discovery:

from httk.core import load

structure = load("example.cif")
# POSCAR, CONTCAR, and compressed variants such as "CONTCAR.bz2" work too.
# CIF loads return ASUStructure; POSCAR/CONTCAR loads return UnitcellStructure.

print("Formula:", structure.formula)
print("Volume:", float(structure.cell.volume))
print("Species at sites:", structure.species_at_sites)
print("Reduced coordinates:", structure.sites.reduced_coords)

Views provide the lazy form: construction checks the source configuration, and parsing waits until the first property is accessed.

from httk.atomistic import ASUStructureView, UnitcellStructureView

structure = UnitcellStructureView("example.cif")
asu = ASUStructureView("example.cif")

For a remote source, pass an explicit httk.core.DatastreamURL consent token.

The split is architectural: httk-atomistic’s I/O layer (httk.atomistic.io) parses file formats and returns neutral payloads, httk-atomistic owns UnitcellStructure and ASUStructure, and httk-core dispatches between them. The adapter registration makes the one-call domain-loading experience work when httk-atomistic is installed. Code that needs the neutral reader result can use the explicit escape hatch load("example.cif", raw=True). Composition and formula properties are part of the structure itself. Providers reuse the same domain projection when exposing a structure through OPTIMADE, so serving or storing it does not require a separate formula calculation. Geometry remains exact until the explicit float(...) used for display.

See the full httk-atomistic loading example in the versioned module documentation listed by the module directory.

See also the Structures and file formats topic page for the current structure vocabulary.