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Schemas for Material Properties

We present throughout this page a list of JSON schemas and example representations concerning properties. The reader is referred to their respective documentation pages, accessible by clicking the headers below, for a review of their underlying physical significance.

Scalar Properties

Total Energy

Total energy contains the total energy of the unit cell.

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{
    "$id": "properties-directory/scalar/total-energy",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "total energy schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/reusable/energy.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "total_energy"
            ]
        }
    }
}

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{
    "name": "total_energy",
    "units": "eV",
    "value": -123.43573079
}

Zero Point Energy

Some residual thermal vibrational energy is left at zero temperature due to quantum effects, and is referred to as Zero Point Energy.

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{
    "$id": "properties-directory/scalar/zero-point-energy",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "zero point energy schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/reusable/energy.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "zero_point_energy"
            ]
        }
    }
}

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{
    "name": "zero_point_energy",
    "units": "eV",
    "value": -123.43573079
}

Fermi Energy

The Fermi energy marks the highest occupied energy level in a solid.

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{
    "$id": "properties-directory/scalar/fermi-energy",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "fermi energy schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/reusable/energy.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "fermi_energy"
            ]
        }
    }
}

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{
    "name": "fermi_energy",
    "units": "eV",
    "value": -1.2
}

Total Energy Contributions

Total energy contributions contains information about the components in the total energy of the unit cell. The contributions available will depend on the type of method and software used.

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{
    "$id": "properties-directory/non-scalar/total-energy-contributions",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "total energy contributions schema",
    "type": "object",
    "properties": {
        "temperatureEntropy": {
            "description": "product of temperature and configurational entropy",
            "type": "object",
            "allOf": [
                {
                    "$ref": "../../core/primitive/scalar.json"
                }
            ],
            "properties": {
                "name": {
                    "enum": [
                        "temperature_entropy"
                    ]
                }
            }
        },
        "harrisFoulkes": {
            "description": "non self-consitent energy based on an input charge density",
            "type": "object",
            "allOf": [
                {
                    "$ref": "../../core/primitive/scalar.json"
                }
            ],
            "properties": {
                "name": {
                    "enum": [
                        "harris_foulkes"
                    ]
                }
            }
        },
        "oneElectron": {
            "description": "kinetic + pseudopotential energy",
            "type": "object",
            "allOf": [
                {
                    "$ref": "../../core/primitive/scalar.json"
                }
            ],
            "properties": {
                "name": {
                    "enum": [
                        "one_electron"
                    ]
                }
            }
        },
        "hartree": {
            "description": "energy due to coulomb potential",
            "type": "object",
            "allOf": [
                {
                    "$ref": "../../core/primitive/scalar.json"
                }
            ],
            "properties": {
                "name": {
                    "enum": [
                        "hartree"
                    ]
                }
            }
        },
        "exchange": {
            "description": "exchange energy",
            "type": "object",
            "allOf": [
                {
                    "$ref": "../../core/primitive/scalar.json"
                }
            ],
            "properties": {
                "name": {
                    "enum": [
                        "exchange"
                    ]
                }
            }
        },
        "exchangeCorrelation": {
            "description": "exchange and correlation energy per particle",
            "type": "object",
            "allOf": [
                {
                    "$ref": "../../core/primitive/scalar.json"
                }
            ],
            "properties": {
                "name": {
                    "enum": [
                        "exchange_correlation"
                    ]
                }
            }
        },
        "ewald": {
            "description": "summation of interaction energies at long length scales due to coloumbic interactions",
            "type": "object",
            "allOf": [
                {
                    "$ref": "../../core/primitive/scalar.json"
                }
            ],
            "properties": {
                "name": {
                    "enum": [
                        "ewald"
                    ]
                }
            }
        },
        "alphaZ": {
            "description": "divergent electrostatic ion interaction in compensating electron gas",
            "type": "object",
            "allOf": [
                {
                    "$ref": "../../core/primitive/scalar.json"
                }
            ],
            "properties": {
                "name": {
                    "enum": [
                        "alphaZ"
                    ]
                }
            }
        },
        "atomicEnergy": {
            "description": "kinetic energy of wavefunctions in the atomic limit",
            "type": "object",
            "allOf": [
                {
                    "$ref": "../../core/primitive/scalar.json"
                }
            ],
            "properties": {
                "name": {
                    "enum": [
                        "atomic_energy"
                    ]
                }
            }
        },
        "eigenvalues": {
            "description": "sum of one electron energies of kinetic, electrostatic, and exchange correlation",
            "type": "object",
            "allOf": [
                {
                    "$ref": "../../core/primitive/scalar.json"
                }
            ],
            "properties": {
                "name": {
                    "enum": [
                        "eigenvalues"
                    ]
                }
            }
        },
        "PAWDoubleCounting2": {
            "description": "double counting correction 2",
            "type": "object",
            "allOf": [
                {
                    "$ref": "../../core/primitive/scalar.json"
                }
            ],
            "properties": {
                "name": {
                    "enum": [
                        "PAW_double-counting_correction_2"
                    ]
                }
            }
        },
        "PAWDoubleCounting3": {
            "description": "double counting correction 3",
            "type": "object",
            "allOf": [
                {
                    "$ref": "../../core/primitive/scalar.json"
                }
            ],
            "properties": {
                "name": {
                    "enum": [
                        "PAW_double-counting_correction_3"
                    ]
                }
            }
        },
        "hartreeFock": {
            "description": "hartree-fock contribution",
            "type": "object",
            "allOf": [
                {
                    "$ref": "../../core/primitive/scalar.json"
                }
            ],
            "properties": {
                "name": {
                    "enum": [
                        "hartree_fock"
                    ]
                }
            }
        },
        "name": {
            "enum": [
                "total_energy_contributions"
            ]
        },
        "units": {
            "$ref": "../../definitions/units.json#/energy"
        }
    }
}

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{
    "PAWDoubleCounting2": {
        "name": "PAW_double-counting_correction_2",
        "value": 12658.30538857
    },
    "PAWDoubleCounting3": {
        "name": "PAW_double-counting_correction_3",
        "value": -12074.85364512
    },
    "alphaZ": {
        "name": "alphaZ",
        "value": 1056.91493097
    },
    "atomicEnergy": {
        "name": "atomic_energy",
        "value": 15740.5725788
    },
    "eigenvalues": {
        "name": "eigenvalues",
        "value": -577.80127102
    },
    "ewald": {
        "name": "ewald",
        "value": 128376.45871064
    },
    "exchange": {
        "name": "exchange",
        "value": 0
    },
    "exchangeCorrelation": {
        "name": "exchange_correlation",
        "value": 41.63693035
    },
    "hartree": {
        "name": "hartree",
        "value": -145344.66902862
    },
    "name": "total_energy_contributions",
    "temperatureEntropy": {
        "name": "temperature_entropy",
        "value": -0.00032545
    },
    "units": "eV"
}

Formation Energy

The Formation energy represents the energy required to create a defect in an otherwise perfect solid structure.

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{
    "$id": "properties-directory/scalar/formation-energy",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "formation energy schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/reusable/energy.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "formation_energy"
            ]
        }
    }
}

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{
    "name": "formation_energy",
    "units": "eV",
    "value": -123.43573079
}

Surface Energy

The energy of a surface can also be computed.

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{
    "$id": "properties-directory/scalar/surface-energy",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "surface energy schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/reusable/energy.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "surface_energy"
            ]
        }
    }
}

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{
    "name": "surface_energy",
    "units": "eV/A^2",
    "value": 0.02
}

Pressure

Pressure contains the average internal pressure of the unit cell.

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{
    "$id": "properties-directory/scalar/pressure",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "pressure",
    "description": "average pressure in unit cell",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/primitive/scalar.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "pressure"
            ]
        },
        "units": {
            "$ref": "../../definitions/units.json#/pressure"
        }
    }
}

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{
    "name": "pressure",
    "units": "kbar",
    "value": -27.345
}

Total Force

This is the total average force present within the crystal structure.

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{
    "$id": "properties-directory/scalar/total-force",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "total forces schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/primitive/scalar.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "total_force"
            ]
        },
        "units": {
            "$ref": "../../definitions/units.json#/force"
        }
    }
}

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{
    "name": "total_force",
    "units": "eV/angstrom",
    "value": 1e-06
}

Valence Band Offset

The valence band offset represents the energy difference of valence bands across a heterostructure interface.

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{
    "$id": "properties-directory/scalar/valence-band-offset",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "valence band offset schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/reusable/energy.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "valence_band_offset"
            ]
        }
    }
}

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{
    "name": "valence_band_offset",
    "units": "eV",
    "value": 0.245
}

Non-Scalar Properties

Bandstructure

Band structure shows the energy of electronic states (bands) as a function of k-point position throughout the cell.

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{
    "$id": "properties-directory/non-scalar/band-structure",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "band structure schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/abstract/2d_plot.json"
        }
    ],
    "properties": {
        "xAxis": {
            "type": "object",
            "properties": {
                "label": {
                    "enum": [
                        "kpoints"
                    ]
                },
                "units": {
                    "$ref": "../../definitions/units.json#/length"
                }
            }
        },
        "yAxis": {
            "type": "object",
            "properties": {
                "label": {
                    "enum": [
                        "energy"
                    ]
                },
                "units": {
                    "$ref": "../../definitions/units.json#/energy"
                }
            }
        },
        "name": {
            "enum": [
                "band_structure"
            ]
        },
        "spin": {
            "description": "spin of each band",
            "type": "array",
            "items": {
                "type": "number",
                "enum": [
                    0.5,
                    -0.5
                ]
            }
        }
    }
}

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{
    "name": "band_structure",
    "spin": [
        0.5,
        0.5,
        0.5,
        0.5
    ],
    "xAxis": {
        "label": "kpoints",
        "units": "crystal"
    },
    "xDataArray": [
        [
            0,
            0,
            0
        ],
        [
            0.5,
            0.5,
            0.5
        ]
    ],
    "yAxis": {
        "label": "energy",
        "units": "eV"
    },
    "yDataSeries": [
        [
            12.1,
            12.5
        ],
        [
            11.1,
            11.5
        ],
        [
            10.1,
            10.5
        ],
        [
            9.5,
            8.5
        ]
    ]
}

Band Gaps

Band gap is the difference in energy from the highest occupied electronic state (Fermi energy at 0K) to the lowest unoccupied state.

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{
    "$id": "properties-directory/non-scalar/band-gaps",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "band gaps schema",
    "description": "contains band gap values",
    "type": "object",
    "properties": {
        "name": {
            "enum": [
                "band_gaps"
            ]
        },
        "values": {
            "type": "array",
            "items": {
                "$ref": "../../core/reusable/band_gap.json"
            }
        },
        "eigenvalues": {
            "type": "array",
            "items": {
                "type": "object",
                "properties": {
                    "kpoint": {
                        "$ref": "../../core/abstract/point.json"
                    },
                    "weight": {
                        "type": "number"
                    },
                    "eigenvalues": {
                        "type": "array",
                        "items": {
                            "type": "object",
                            "properties": {
                                "spin": {
                                    "type": "number"
                                },
                                "energies": {
                                    "type": "array"
                                },
                                "occupations": {
                                    "type": "array"
                                }
                            }
                        }
                    }
                }
            }
        }
    },
    "required": [
        "name"
    ]
}

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{
    "name": "band_gaps",
    "values": [
        {
            "kpointConduction": [
                0,
                0,
                0
            ],
            "kpointValence": [
                0,
                0,
                0
            ],
            "type": "direct",
            "units": "rydberg",
            "value": 0.0947
        },
        {
            "type": "indirect",
            "units": "rydberg",
            "value": 0.0
        }
    ]
}

Electronic Density of States

Density of states contains information on the number of electronic states as a function of energy. It may include the atom resolved partial density of states and electron states in some cases. In addition it may also contain information about each atom’s spin state as well.

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{
    "$id": "properties-directory/non-scalar/density-of-states",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "density of states schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/abstract/2d_plot.json"
        }
    ],
    "properties": {
        "xAxis": {
            "type": "object",
            "properties": {
                "label": {
                    "enum": [
                        "energy"
                    ]
                },
                "units": {
                    "$ref": "../../definitions/units.json#/energy"
                }
            }
        },
        "yAxis": {
            "type": "object",
            "properties": {
                "label": {
                    "enum": [
                        "density of states"
                    ]
                },
                "units": {
                    "$ref": "../../definitions/units.json#/electronicDOS"
                }
            }
        },
        "name": {
            "enum": [
                "density_of_states"
            ]
        },
        "legend": {
            "type": "array",
            "items": {
                "type": "object",
                "properties": {
                    "element": {
                        "description": "chemical element",
                        "type": "string"
                    },
                    "index": {
                        "description": "index inside sub-array of atoms of the same element type",
                        "type": "integer"
                    },
                    "electronicState": {
                        "description": "electronic character and shell of PDOS, such as `1s` or `s`, or `total`",
                        "type": "string",
                        "pattern": "^([1-5]{1})?(s|p|d|f|g).*$"
                    },
                    "spin": {
                        "description": "spin of the electronic state",
                        "type": "number",
                        "enum": [
                            0.5,
                            -0.5
                        ]
                    }
                }
            }
        }
    }
}

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{
    "legend": [
        {
            "electronicState": "2s",
            "element": "C",
            "index": 1,
            "spin": 0.5
        },
        {
            "electronicState": "2p",
            "element": "C",
            "index": 2,
            "spin": 0.5
        }
    ],
    "name": "density_of_states",
    "xAxis": {
        "label": "energy",
        "units": "eV"
    },
    "xDataArray": [
        [
            0,
            0,
            0
        ],
        [
            0.5,
            0.5,
            0.5
        ]
    ],
    "yAxis": {
        "label": "density of states",
        "units": "states/unitcell"
    },
    "yDataSeries": [
        [
            12.1,
            12.5
        ],
        [
            11.1,
            11.5
        ],
        [
            10.1,
            10.5
        ],
        [
            9.5,
            8.5
        ]
    ]
}

File Content

Tags a file for display on the results tab of the web-app.

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{
    "$id": "properties-directory/non-scalar/file-content",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "file_content",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/reusable/file_metadata.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "file_content"
            ]
        },
        "filetype": {
            "description": "What kind of file this is, e.g. image / text",
            "type": "string",
            "enum": [
                "image",
                "text",
                "csv"
            ],
            "$comment": "isGenerative:true"
        },
        "objectData": {
            "$ref": "../../core/reusable/object_storage_container_data.json"
        }
    },
    "required": [
        "name",
        "objectData"
    ]
}

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{
    "name": "file_content",
    "basename": "my_json.json",
    "filetype": "text",
    "objectData": {
        "...": "include(../../core/reusable/object_storage_container_data.json)"
    }
}

Reaction Energy Profile

The energy profile of a chemical reaction is a representation of its energetic pathway, followed by the reactants as they are transformed into products.

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{
    "$id": "properties-directory/non-scalar/reaction-energy-profile",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "reaction energy profile schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/abstract/2d_plot.json"
        }
    ],
    "properties": {
        "xAxis": {
            "type": "object",
            "properties": {
                "label": {
                    "enum": [
                        "reaction coordinate"
                    ]
                }
            }
        },
        "yAxis": {
            "type": "object",
            "properties": {
                "label": {
                    "enum": [
                        "energy"
                    ]
                },
                "units": {
                    "$ref": "../../definitions/units.json#/energy"
                }
            }
        },
        "name": {
            "enum": [
                "reaction_energy_profile"
            ]
        }
    }
}

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{
    "name": "reaction_energy_profile",
    "xAxis": {
        "label": "reaction coordinate"
    },
    "xDataArray": [
        0.0,
        0.1932731666,
        0.3596118308,
        0.4999998753,
        0.640387977,
        0.8067267116,
        1.0
    ],
    "yAxis": {
        "label": "energy",
        "units": "eV"
    },
    "yDataSeries": [
        [
            0.0,
            0.0336637211,
            0.1282952413,
            0.2032895454,
            0.1282953846,
            0.0336637671,
            -5.3e-09
        ]
    ]
}

Reaction Energy Barrier

The Reaction Energy Barrier marks the highest energy state encountered during the course of the progress of a chemical reaction.

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{
    "$id": "properties-directory/scalar/reaction-energy-barrier",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "reaction energy barrier schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/reusable/energy.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "reaction_energy_barrier"
            ]
        }
    }
}

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{
    "name": "reaction_energy_barrier",
    "units": "eV",
    "value": -123.43573079
}

Phonon Dispersions

Lattice vibrations can be plotted in the form of phonon frequency dispersion plots across the reciprocal k-space of the crystal structure.

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{
    "$id": "properties-directory/non-scalar/phonon-dispersions",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "phonon band structure schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/abstract/2d_plot.json"
        }
    ],
    "properties": {
        "xAxis": {
            "type": "object",
            "properties": {
                "label": {
                    "enum": [
                        "qpoints"
                    ]
                },
                "units": {
                    "$ref": "../../definitions/units.json#/length"
                }
            }
        },
        "yAxis": {
            "type": "object",
            "properties": {
                "label": {
                    "enum": [
                        "frequency"
                    ]
                },
                "units": {
                    "$ref": "../../definitions/units.json#/frequency"
                }
            }
        },
        "name": {
            "enum": [
                "phonon_dispersions"
            ]
        }
    }
}

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{
    "name": "phonon_dispersions",
    "xAxis": {
        "label": "qpoints",
        "units": "crystal"
    },
    "xDataArray": [
        [
            0,
            0,
            0
        ],
        [
            0.5,
            0.05,
            0.05
        ]
    ],
    "yAxis": {
        "label": "frequency",
        "units": "cm-1"
    },
    "yDataSeries": [
        [
            -6e-06,
            -6e-06,
            -5e-06,
            734.596987,
            734.618837,
            734.618837
        ],
        [
            -6.859784,
            -6.859784,
            36.443014,
            730.782803,
            731.143013,
            731.143013
        ]
    ]
}

Phonon Density of States

The Density of States for phonons can also be computed.

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{
    "$id": "properties-directory/non-scalar/phonon-dos",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "Phonon density of states schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/abstract/2d_plot.json"
        }
    ],
    "properties": {
        "xAxis": {
            "type": "object",
            "properties": {
                "label": {
                    "enum": [
                        "frequency"
                    ]
                },
                "units": {
                    "$ref": "../../definitions/units.json#/frequency"
                }
            }
        },
        "yAxis": {
            "type": "object",
            "properties": {
                "label": {
                    "enum": [
                        "Phonon DOS"
                    ]
                },
                "units": {
                    "$ref": "../../definitions/units.json#/phononDOS"
                }
            }
        },
        "name": {
            "enum": [
                "phonon_dos"
            ]
        }
    }
}

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{
    "name": "phonon_dos",
    "xAxis": {
        "label": "frequency",
        "units": "cm-1"
    },
    "xDataArray": [
        [
            565.0,
            566.0,
            567.0,
            568.0,
            569.0,
            570.0,
            571.0,
            572.0,
            573.0
        ]
    ],
    "yAxis": {
        "label": "Phonon DOS",
        "units": "states/cm-1"
    },
    "yDataSeries": [
        [
            0.0001433,
            0.00011382,
            8.7721e-05,
            6.502e-05,
            4.5713e-05,
            2.9799e-05,
            1.7279e-05,
            8.1527e-06,
            2.4197e-06
        ]
    ]
}

Stress Tensor

Stress tensor contains a 3x3 matrix of the stress components of the unit cell.

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{
    "$id": "properties-directory/non-scalar/stress-tensor",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "stress tensor schema",
    "type": "object",
    "properties": {
        "value": {
            "$ref": "../../core/abstract/3d_tensor.json"
        },
        "name": {
            "enum": [
                "stress_tensor"
            ]
        },
        "units": {
            "$ref": "../../definitions/units.json#/pressure"
        }
    }
}

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{
    "name": "stress_tensor",
    "units": "kbar",
    "value": [
        [
            3,
            0,
            0
        ],
        [
            0,
            3,
            0
        ],
        [
            0,
            0,
            3
        ]
    ]
}

Workflow

Some jobs can result in the generation of new workflows, which will be placed in the user's account.

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{
    "$id": "workflow",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "workflow schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "workflow/base.json"
        }
    ],
    "properties": {
        "subworkflows": {
            "description": "Array of subworkflows. Subworkflow can be an instance of workflow to allow for nesting",
            "type": "array",
            "items": {
                "allOf": [
                    {
                        "$ref": "workflow/subworkflow.json"
                    }
                ]
            }
        },
        "units": {
            "description": "Contains the Units of the Workflow",
            "type": "array",
            "items": {
                "$ref": "workflow/unit.json"
            }
        }
    },
    "required": [
        "units",
        "subworkflows"
    ]
}

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{
    "_id": "FPjAaKfuYAL7tiHbm",
    "createdAt": "2018-11-19 06:41:46.877Z",
    "creator": {
        "...": "include(system/creator.json)"
    },
    "exabyteId": "qKtTzu9utCo6ac4n7",
    "hash": "f4fd707d2e47c15f8d786cf159040954",
    "isDefault": true,
    "name": "workflow",
    "owner": {
        "...": "include(system/owner.json)"
    },
    "properties": [
        "band_structure"
    ],
    "schemaVersion": "0.2.0",
    "slug": "workflow",
    "subworkflows": [
        {
            "...": "include(workflow/subworkflow.json)"
        }
    ],
    "tags": [
        "workflow"
    ],
    "units": [
        {
            "_id": "LCthJ6E2QabYCZqf4",
            "flowchartId": "05c362dc27ff1bb98d16fd60",
            "type": "subworkflow",
            "name": "subworkflow unit"
        }
    ]
}

Elemental Properties

Atomic Radius

The atomic radius represents the average distance between the nucleus of an atom and the edges of its surrounding electron cloud.

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{
    "$id": "properties-directory/elemental/atomic-radius",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "atomic radius",
    "description": "atomic radius",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/primitive/scalar.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "atomic_radius"
            ]
        },
        "units": {
            "$ref": "../../definitions/units.json#/length"
        }
    }
}

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{
    "name": "atomic_radius",
    "value": 4
}

Electronegativity

The electronegativity describes the capacity of an atom to attract the electrons involved in chemical bonding.

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{
    "$id": "properties-directory/elemental/electronegativity",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "electronegativity",
    "description": "electronegativity for the element (Pauling scale)",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/primitive/scalar.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "electronegativity"
            ]
        }
    }
}

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{
    "name": "electronegativity",
    "value": 1.1
}

Ionization Potential

The ionization energy (or potential) measures the energy required to strip an atom from its most loosely bound valence electron.

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{
    "$id": "properties-directory/elemental/ionization-potential",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "ionization potential",
    "description": "ionization potential for the element",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/primitive/scalar.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "ionization_potential"
            ]
        },
        "units": {
            "$ref": "../../definitions/units.json#/energy"
        }
    }
}

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{
    "name": "ionization_potential",
    "value": 7.7
}

Structural Properties

Atomic Forces

Forces may exist between atoms in a crystal structure if they are displaced away from their equilibrium configuration.

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{
    "$id": "properties-directory/structural/atomic-forces",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "atomic forces",
    "description": "coordinates of atoms by ids, vector, unitless",
    "type": "object",
    "properties": {
        "name": {
            "enum": [
                "atomic_forces"
            ]
        },
        "values": {
            "$ref": "../../core/reusable/atomic_vectors.json"
        },
        "units": {
            "$ref": "../../definitions/units.json#/force"
        }
    }
}

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{
    "name": "atomic_forces",
    "units": "eV/bohr",
    "values": [
        {
            "id": 1,
            "value": [
                -3.9e-07,
                -2.4e-07,
                0.0
            ]
        },
        {
            "id": 2,
            "value": [
                3.9e-07,
                2.4e-07,
                0.0
            ]
        }
    ]
}

Atomic Coordinates

Contains information about the coordinates of atoms within the unit cell by id.

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{
    "$id": "properties-directory/structural/basis/atomic-coordinates",
    "title": "atomic coordinates",
    "description": "coordinates of atoms by ids, vector, unitless",
    "type": "object",
    "properties": {
        "name": {
            "enum": [
                "atomic_coordinates"
            ]
        },
        "values": {
            "type": "array",
            "items": {
                "$ref": "atomic_coordinate.json"
            }
        },
        "units": {
            "$ref": "../../../definitions/units.json#/length"
        }
    }
}

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{
    "name": "atomic_coordinates",
    "values": [
        {
            "id": 1,
            "value": [
                0,
                0,
                0
            ]
        },
        {
            "id": 2,
            "value": [
                0.25,
                0.25,
                0.25
            ]
        }
    ]
}

Atomic Elements

Contains an array of the elements in the unit cell and the atom id’s association with each atom.

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{
    "$id": "properties-directory/structural/basis/atomic-element",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "atomic elements",
    "description": "elements of atoms by ids, string, unitless",
    "type": "object",
    "properties": {
        "id": {
            "type": "number"
        },
        "value": {
            "type": "string"
        },
        "occurrence": {
            "description": "Occurrence is for fractional occupations",
            "type": "number"
        },
        "oxidationState": {
            "type": "number"
        }
    },
    "required": [
        "id",
        "value"
    ]
}

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{
    "id": 1,
    "value": "Si"
}

Atomic Constraints

Contains information about the spatial constraints on the movement of atoms.

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{
    "$id": "properties-directory/structural/basis/atomic-constraints",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "atomic constraints",
    "description": "atomic constraints schema",
    "type": "object",
    "properties": {
        "name": {
            "enum": [
                "atomic_constraints"
            ]
        },
        "values": {
            "$ref": "../../../core/reusable/atomic_vectors.json"
        }
    }
}

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{
    "name": "atomic_constraints",
    "values": [
        {
            "id": 1,
            "value": [
                true,
                false,
                true
            ]
        },
        {
            "id": 2,
            "value": [
                false,
                false,
                true
            ]
        }
    ]
}

Basis

Basis defines elemental and geometrical constitution of the unit cell.

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{
    "$id": "properties-directory/structural/basis",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "basis schema",
    "type": "object",
    "properties": {
        "elements": {
            "type": "array",
            "items": {
                "$ref": "basis/atomic_element.json"
            }
        },
        "labels": {
            "description": "Optional numeric label (e.g., 1, 2, as in Fe1, Fe2) to distinguish same atomic species to attach different spin magnetic moment.",
            "type": "array",
            "items": {
                "properties": {
                    "id": {
                        "type": "number"
                    },
                    "value": {
                        "type": "number"
                    }
                }
            }
        },
        "coordinates": {
            "type": "array",
            "items": {
                "$ref": "basis/atomic_coordinate.json"
            }
        },
        "name": {
            "type": "string"
        },
        "units": {
            "type": "string"
        },
        "bonds": {
            "$ref": "basis/bonds.json"
        }
    },
    "required": [
        "elements",
        "coordinates"
    ]
}

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{
    "bonds": [
        {
            "...": "include(basis/bonds.json)"
        }
    ],
    "coordinates": [
        {
            "...": "include(basis/atomic_coordinate.json)"
        }
    ],
    "elements": [
        {
            "...": "include(basis/atomic_element.json)"
        }
    ],
    "name": "basis",
    "units": "crystal"
}

Bravais Lattice

Lattice Bravais holds information about the three-dimensional periodic structure specified implicitly through lengths and angles between lattice vectors, and their units.

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{
    "$id": "properties-directory/structural/lattice/lattice-bravais",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "lattice implicit schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../../core/primitive/3d_lattice.json"
        }
    ],
    "properties": {
        "type": {
            "description": "Bravais lattice type in short notation",
            "$ref": "type_enum.json"
        },
        "units": {
            "type": "object",
            "properties": {
                "length": {
                    "type": "string",
                    "enum": [
                        "angstrom",
                        "bohr"
                    ]
                },
                "angle": {
                    "type": "string",
                    "enum": [
                        "degree",
                        "radian"
                    ]
                }
            }
        }
    },
    "required": [
        "type"
    ]
}

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{
    "a": 5.14,
    "alpha": 90.0,
    "b": 5.14,
    "beta": 90.0,
    "c": 5.14,
    "gamma": 90.0,
    "type": "CUB",
    "units": {
        "angle": "degree",
        "length": "angstrom"
    }
}

Lattice Vectors

Lattice vectors holds information about the three-dimensional periodic structure explicitly, by specifying the three lattice vectors and their units.

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{
    "$id": "properties-directory/structural/lattice/lattice-vectors",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "lattice explicit unit",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../../core/abstract/3d_vector_basis.json"
        }
    ],
    "properties": {
        "alat": {
            "description": "lattice parameter for fractional coordinates",
            "type": "number",
            "default": 1
        },
        "units": {
            "$ref": "../../../definitions/units.json#/length"
        }
    }
}

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{
    "a": [
        5.0,
        0.000121312,
        0.000131415
    ],
    "alat": 1.0,
    "b": [
        0.000121312,
        5.0,
        0.000121314
    ],
    "c": [
        0.000121313,
        0.000121312,
        5.0
    ],
    "units": "angstrom"
}

Density

The Density of the material is defined by the sum of the atomic masses within the unit cell, divided by its volume.

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{
    "$id": "properties-directory/structural/density",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "density schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/primitive/scalar.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "density"
            ]
        },
        "units": {
            "enum": [
                "g/cm^3"
            ]
        }
    }
}

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{
    "name": "density",
    "units": "g/cm^3",
    "value": 2.33
}

Elemental Ratio

The elemental ratio is given by the fraction of all atoms in a crystal which are composed of a certain element.

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{
    "$id": "properties-directory/structural/elemental-ratio",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "elemental-ratio",
    "description": "ration of this element in the compound",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/primitive/scalar.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "elemental_ratio"
            ]
        },
        "value": {
            "type": "number",
            "minimum": 0,
            "maximum": 1
        },
        "element": {
            "type": "string",
            "description": "the element this ratio is for"
        }
    }
}

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{
    "element": "Si",
    "name": "elemental_ratio",
    "value": 0.71
}

InChI

The International Chemical Identifier1 used to identify molecules.

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{
    "$id": "properties-directory/structural/inchi",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "InChI representation schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/primitive/string.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "inchi"
            ]
        }
    }
}

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{
    "name": "inchi",
    "value": "1S/C6H6/c1-2-4-6-5-3-1/h1-6H"
}

InChIKey

The fixed-length non-human readable string derived from an InChI.

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{
    "$id": "properties-directory/structural/inchi-key",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "InChI key representation schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/primitive/string.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "inchi_key"
            ]
        }
    }
}

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{
    "name": "inchi_key",
    "value": "UHOVQNZJYSORNB-UHFFFAOYSA-N"
}

Magnetic Moments

The magnetic moment of ferromagnetic materials can also be computed.

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{
    "$id": "properties-directory/structural/magnetic-moments",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "magnetic moments",
    "description": "magnetization on each ion",
    "type": "object",
    "properties": {
        "name": {
            "enum": [
                "magnetic_moments"
            ]
        },
        "values": {
            "$ref": "../../core/reusable/atomic_vectors.json"
        },
        "units": {
            "$ref": "../../definitions/units.json#/magnetic"
        }
    }
}

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{
    "name": "magnetic_moments",
    "units": "uB",
    "values": [
        {
            "id": 1,
            "value": [
                0.0,
                0.0,
                1.235
            ]
        },
        {
            "id": 2,
            "value": [
                0.0,
                0.0,
                -1.235
            ]
        }
    ]
}

P Norm

The P norm measures how homogeneous a material is in terms of its chemical composition.

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{
    "$id": "properties-directory/structural/p-norm",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "p_norm",
    "description": "https://en.wikipedia.org/wiki/Norm_(mathematics)#p-norm",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/primitive/scalar.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "p-norm"
            ]
        },
        "degree": {
            "type": "integer",
            "description": "degree of the dimensionality of the norm"
        }
    }
}

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{
    "degree": 10,
    "name": "p-norm",
    "value": 0.71
}

Symmetry

The symmetry of the structure, indicating the point group and space group.

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{
    "$id": "properties-directory/structural/symmetry",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "symmetry schema",
    "type": "object",
    "properties": {
        "pointGroupSymbol": {
            "description": "point group symbol in Schoenflies notation",
            "type": "string"
        },
        "spaceGroupSymbol": {
            "description": "space group symbol in Hermann–Mauguin notation",
            "type": "string"
        },
        "tolerance": {
            "type": "object",
            "description": "tolerance used for symmetry calculation",
            "allOf": [
                {
                    "$ref": "../../core/primitive/scalar.json"
                }
            ],
            "properties": {
                "units": {
                    "enum": [
                        "angstrom"
                    ]
                }
            }
        },
        "name": {
            "enum": [
                "symmetry"
            ]
        }
    }
}

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{
    "name": "symmetry",
    "pointGroupSymbol": "C2v",
    "spaceGroupSymbol": "Fd-3m",
    "tolerance": {
        "units": "angstrom",
        "value": 0.3
    }
}

Volume

The volume of the unit cell is given by the scalar triple product of the lattice vectors.

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{
    "$id": "properties-directory/structural/volume",
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "volume schema",
    "type": "object",
    "allOf": [
        {
            "$ref": "../../core/primitive/scalar.json"
        }
    ],
    "properties": {
        "name": {
            "enum": [
                "volume"
            ]
        },
        "units": {
            "enum": [
                "angstrom^3"
            ]
        }
    }
}

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{
    "name": "volume",
    "units": "angstrom^3",
    "value": 131.1
}

  1. Wikipedia - International Chemical Identifier (Website) ↩