Field definitions
These are the prefixed OPTIMADE field names usable in search filters and sort expressions; each links to its full property definition.
Field Description _anyterial_avg_spin_splittingThe Brillouin-zone average of the per-k-point largest spin splitting, evaluated within an energy window of plus or minus 3 eV around the Fermi level. _anyterial_classificationThe source classification assigned to the material by the altermagnet material store from the kinds of its linked symmetry-variant sources. _anyterial_electronic_typeA qualitative classification of the electronic structure of the material. _anyterial_elementsThe alphabetized chemical element symbols extracted from the formula recorded by the altermagnet screening workflow. _anyterial_formulaThe chemical formula recorded by the altermagnet screening workflow, served verbatim as a display string. _anyterial_icsd_idsThe ordered, deduplicated Inorganic Crystal Structure Database identifiers collected from the material's linked symmetry variants. _anyterial_magndata_variantsThe ordered list of symmetry variants resolved for the material from its linked MAGNDATA records, one item per record and symmetry-detection tolerance. _anyterial_magnetic_phaseThe magnetic phase assigned to the material by collinear/noncollinear symmetry analysis. _anyterial_magnetic_phasesThe full ordered, deduplicated magnetic-phase list collected from the material's linked symmetry variants. _anyterial_max_spin_splittingThe largest spin splitting of the electronic bands found within an energy window of plus or minus 3 eV around the Fermi level. _anyterial_min_crustal_abundanceThe minimum crustal abundance among the constituent elements of the material, given in parts per million by mass. _anyterial_parent_spacegroupsThe full ordered, deduplicated parent-space-group list collected from the material's linked symmetry variants. _anyterial_screening_rankThe material's ordinal position in the published high-throughput screening table, starting at 1. _anyterial_search_textThe normalized lowercase free-text aggregate maintained by the altermagnet material store, concatenating the formula, MAGNDATA identifiers, space groups, elements, magnetic phases, wave classes, and the source classification. _anyterial_space_groupThe space-group display string recorded by the altermagnet screening workflow, served verbatim. _anyterial_space_group_searchThe screening space-group display string normalized by stripping surrounding whitespace and lowercasing. _anyterial_spin_splitting_fractionA dimensionless relative spin-splitting measure in the range 0 to 1. _anyterial_wave_classThe simplified spin-momentum wave class of the altermagnetic order. _anyterial_wave_classesThe full ordered, deduplicated spin-momentum wave-class list collected from the material's linked symmetry variants. _httk_basis_precisionThe absolute precision of a stated length, in ångström. _httk_centring_typeThe lattice centring symbol for the crystallographic setting. _httk_chargeThe explicitly assigned net charge of the whole structure, as a dimensionless charge number, i.e., the charge in units of the elementary charge. _httk_coordinate_precisionThe absolute precision of a set of fractional coordinates, in fractional units. _httk_crystal_systemThe crystal system of the space group or point group. _httk_custom_figuresData-only figure metadata for this deployment's fixed band-structure, crystal-structure, and Brillouin-zone figures. _httk_dft_band_gapThe Kohn-Sham band gap of a material from a density-functional-theory (DFT) calculation, given in electronvolts. Its value depends on the computational method and exchange-correlation functional used. _httk_hall_entryNormalized Hall-table entry key used internally by the generated datasets. _httk_is_reference_settingBoolean flag indicating whether this Hall setting is the selected reference setting for its International Tables space-group number. _httk_magndata_idsThe identifiers of MAGNDATA magnetic-structure entries associated with a material. _httk_magnetic_space_group_bnsThe magnetic space group of a material in Belov-Neronova-Smirnova (BNS) notation. _httk_setting_it_ncInternational Tables setting identifier in `n:c` notation. _httk_setting_transformAn affine transformation acting on fractional crystallographic coordinates. _httk_site_momentsThe magnetic moment vector of each site, in Cartesian coordinates and Bohr magnetons. assembliesA description of groups of sites that are statistically correlated. cartesian_site_positionsCartesian positions of each site in the structure. chemical_formula_anonymousThe anonymous formula is the chemical_formula_reduced, but where the elements are instead first ordered by their chemical proportion number, and then, in order left to right, replaced by anonymous symbols A, B, C, ..., Z, Aa, Ba, ..., Za, Ab, Bb, ... and so on. chemical_formula_descriptiveThe chemical formula for a structure as a string in a form chosen by the API implementation. chemical_formula_hillThe chemical formula for a structure in [Hill form](https://dx.doi.org/10.1021/ja02046a005) with element symbols followed by integer chemical proportion numbers. The proportion number MUST be omitted if it is 1. chemical_formula_reducedThe reduced chemical formula for a structure as a string with element symbols and integer chemical proportion numbers. dimension_typesList of three integers describing the periodicity of the boundaries of the unit cell. For each direction indicated by the three lattice_vectors, this list indicates if the direction is periodic (value 1) or non-periodic (value 0). Note: the elements in this list each refer to the direction of the corresponding entry in lattice_vectors and not the Cartesian x, y, z directions. elementsThe chemical symbols of the different elements present in the structure. elements_ratiosRelative proportions of different elements in the structure. fractional_site_positionsFractional coordinates (positions) of each site in the structure. idA unique string referencing a specific entry in the database. immutable_idThe entry's immutable ID (e.g., a UUID). last_modifiedDate and time representing when the entry was last modified. lattice_vectorsThe three lattice vectors in Cartesian coordinates, in ångström (Å). nelementsNumber of different elements in the structure as an integer. nperiodic_dimensionsAn integer specifying the number of periodic dimensions in the structure, equivalent to the number of non-zero entries in `dimension_types`. nsitesAn integer specifying the length of the `cartesian_site_positions` property. optimization_typeA string that classifies the type of optimization that has resulted in the structural data. site_coordinate_spanIndicates the extent of the material (crystal) described in the response.
In particular, properties `cartesian_site_positions` and `fractional_site_positions` MUST contain all sites *belonging* to the described extent. site_coordinate_span_descriptionHuman-readable semi-formal characterization of the coordinate span when the `site_coordinate_span` property has value `other`. space_group_it_numberSpace group number for the structure assigned by the International Tables for Crystallography Vol. A. space_group_symbol_hallA Hall space group symbol representing the symmetry of the structure as defined in Hall, S. R. (1981), Acta Cryst. A37, 517-525 and erratum (1981), A37, 921. space_group_symbol_hermann_mauguinA human- and machine-readable string containing the short Hermann-Mauguin (H-M) symbol which specifies the space group of the structure in the response. space_group_symbol_hermann_mauguin_extendedA human- and machine-readable string containing the extended Hermann-Mauguin (H-M) symbol which specifies the space group of the structure in the response. space_group_symmetry_operations_xyzA list of symmetry operations given as general position x, y and z coordinates in algebraic form. speciesA list describing the species of the sites of this structure. Species can represent pure chemical elements, virtual-crystal atoms representing a statistical occupation of a given site by multiple chemical elements, and/or a location to which there are attached atoms, i.e., atoms whose precise location are unknown beyond that they are attached to that position (frequently used to indicate hydrogen atoms attached to another element, e.g., a carbon with three attached hydrogens might represent a methyl group, -CH3). species_at_sitesName of the species at each site (where values for sites are specified with the same order of the property `cartesian_site_positions`). The properties of the species are found in the property `species`. structure_featuresA list of strings that flag which special features are used by the structure. typeThe name of the type of an entry. wyckoff_positionsA list of Wyckoff symbols of sites (where values for sites are specified with the same order of the property `cartesian_site_positions` and/or `fractional_site_positions`).