Idealised Rock-Salt Structure — Crystallographic CIF (.cif)
A single-data-block CIF describing an idealised rock-salt lattice: cell parameters, space group, a symmetry-operation loop and an atom-site loop with fractional coordinates and occupancies. The '?' in the temperature field is CIF's marker for unknown, which is not the same as an empty value.
data_rock_salt_idealised
_audit_creation_method 'Novus Examples synthetic fixture'
_chemical_name_common 'idealised rock-salt structure model'
_chemical_formula_sum 'Cl1 Na1'
_chemical_formula_weight 58.44
_cell_length_a 5.64020
_cell_length_b 5.64020
_cell_length_c 5.64020
_cell_angle_alpha 90.0000
_cell_angle_beta 90.0000
_cell_angle_gamma 90.0000
_cell_volume 179.426
_cell_formula_units_Z 4
_space_group_name_H-M_alt 'F m -3 m'
_space_group_IT_number 225
_diffrn_ambient_temperature ?
loop_
_space_group_symop_operation_xyz
'x, y, z'
'-x, -y, z'
'-x, y, -z'
'x, -y, -z'
'z, x, y'
'y, z, x'
loop_
_atom_site_label
_atom_site_type_symbol
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_occupancy
_atom_site_U_iso_or_equiv
Na1 Na 0.00000 0.00000 0.00000 1.000 0.01500
Cl1 Cl 0.50000 0.00000 0.00000 1.000 0.01500
# This is a textbook lattice model, not a refined experimental structure.
Specifications
- Format
- CIF 1.1
- Data Blocks
- 1
- Loops
- 2
- Atom Sites
- 2
- Symmetry Operations
- 6
- Cell Length Angstrom
- 5.6402
- Space Group Number
- 225
- Unknown Value Marker
- ?
- Idealised Model
- true
Testing contract
Expected to pass- Scenario
- Parse the data block, both loops, and the tags with and without values, then compute the cell volume from a, b and c.
- Expected result
- Two loops resolve with six symmetry operations and two atom sites, the computed volume matches the declared 179.426 cubic angstrom, and _diffrn_ambient_temperature reads as unknown rather than as the literal string '?'.
What is a .cif file?
CIF (Crystallographic Information File) is the IUCr's standard text format for crystal structures. It is a tagged plain-text format in which `_data_name value` pairs and `loop_` blocks carry unit-cell parameters, symmetry operations, atom sites with fractional coordinates and occupancies, and full experimental provenance. mmCIF, its macromolecular profile, is now the archival format of the Protein Data Bank.
How to use this file
Use an example .cif file to test crystallography parsers and structure viewers, exercising loop_ construct handling, quoted and multi-line semicolon-delimited values, and the reconstruction of Cartesian coordinates from fractional ones and the cell parameters.
How to use this file for testing
“Idealised Rock-Salt Structure — Crystallographic CIF (.cif)” is a deterministic Novus Examples fixture for Scientific data, Editor testing. Citation catalogs (BibTeX, RIS), chemistry structures (MDL Molfile, PDB), and gridded binary data (NetCDF, FITS) — for testing reference managers, molecule viewers, and scientific-data loaders.
Documented properties for this file: CIF 1.1. Compare results against paired or grouped companions on this page when present (clean↔damaged, searchable↔scanned, or format twins) so scores stay reproducible across runs.
Download the file once, keep the path stable in CI or local scripts, and treat the spec table as the contract: dimensions, seeds, field lists, and roles are intentional. Corrupt or invalid samples are labelled as such — expect parsers to fail loudly rather than silently accept them.
Scientific fixtures are small, valid, and fully synthetic — no real organism, patient, sample, or observation. Point your parser or loader at the file and check it reads the documented records, variables, or headers; binary formats ship a readable twin or metadata listing for comparison.
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