iodata.formats.json_qcschema module¶

QCSchema JSON file format.

QCSchema defines four different subschema:

Molecule: specifying a molecular system
Input: specifying QC program input for a specific Molecule
Output: specifying QC program output for a specific Molecule
Basis: specifying a basis set for a specific Molecule

General Usage¶

The QCSchema format is intended to be a catch-all file format for storing and sharing QC calculation data. Due to the wide number of possibilities of the data contained in a single file, not every field in a QCSchema file directly corresponds to an IOData attribute. For example, qcschema_output files allow for many fields capturing different energy contributions, especially for coupled-cluster calculations. To accommodate this fact, IOData does not always assume the intent of the user; instead, IOData ensures that every field in the file is stored in a structured manner. When a QCSchema field does not correspond to an IOData attribute, that data is instead stored in the extra dict, in a dictionary corresponding to the subschema where that data was found. In cases where multiple subschema contain the relevant field (e.g. the Output subschema contains the entirety of the Input subschema), the data will be found in the smallest subschema (for the example above, in IOData.extra["input"], not IOData.extra["output"]).

Dumping an IOData instance to a QCSchema file involves adding relevant required (and optional, if needed) fields to the necessary dictionaries in the extra dict. One exception is the provenance field: if the only desired provenance data is the creation of the file by IOData, that data will be added automatically.

The following sections will describe the requirements of each subschema and the behaviour to expect from IOData when loading in or dumping out a QCSchema file.

Schema Definitions¶

Provenance Information¶

The provenance field contains information about how the associated QCSchema object and its attributes were generated, provided, and manipulated. A provenance entry expects these fields:

Field	Description
creator	Required. The program that generated, provided, or manipulated this file.
version	The version of the creator.
routine	The routine of the creator.

In QCElemental, only a single provenance entry is permitted. When generating a QCSchema file for use with QCElemental, the easiest way to ensure compliance is to leave the provenance field blank, to allow the dump_one function to generate the correct provenance information. However, allowing only one entry for provenance information limits the ability to properly trace a file through several operations during complex workflows. With this in mind, IOData supports an enhanced provenance field, in the form of a list of provenance entries, with new entries appended to the end of the list.

Molecule Schema¶

The qcschema_molecule subschema describes a molecular system, and contains the data necessary to specify a molecular system and support I/O and manipulation processes.

The following is an example of a minimal qcschema_molecule file:

{
  "schema_name": "qcschema_molecule",
  "schema_version": 2,
  "symbols":  ["Li", "Cl"],
  "geometry": [0.000000, 0.000000, -1.631761, 0.000000, 0.000000, 0.287958],
  "molecular_charge": 0,
  "molecular_multiplicity": 1,
  "provenance": {
    "creator": "HORTON3",
    "routine": "Manual validation"
  }
}

The required fields and corresponding types for a qcschema_molecule file are:

Field	Type	IOData attr.	Description
schema_name	str	N/A	The name of the QCSchema subschema. Fixed as `qcschema_molecule`.
schema_version	str	N/A	The version of the subschema specification. 2.0 is the current version.
symbols	list(N_at)	`atnums`	An array of the atomic symbols for the system.
geometry	list(3*N_at)	`atcoords`	An ordered array of XYZ atomic coordinates, corresponding to the order of `symbols`. The first three elements correspond to atom one, the second three to atom two, etc.
molecular_charge	float	`charge`	The net electrostatic charge of the molecule. Some writers assume a default of 0.
molecular_multiplicity	int	`spinpol`	The total multiplicity of this molecule. Some writers assume a default of 1.
provenance	dict or list	N/A	Information about the file was generated, provided, and manipulated. See Provenance section above for more details.

Note: N_at corresponds to the number of atoms in the molecule, as defined by the length of symbols.

The optional fields and corresponding types for a qcschema_molecule file are:

Field	Type	IOData attr.	Description
atom_labels	list(N_at)	N/A	Additional per-atom labels. Typically used for model conversions, not user assignment. The indices of this array correspond to the `symbols` ordering.
atomic_numbers	list(N_at)	`atnums`	An array of atomic numbers for each atom. Typically inferred from `symbols`.
comment	str	N/A	Additional comments for this molecule. These comments are intended for user information, not any computational tasks.
connectivity	list	`bonds`	The connectivity information between each atom in the `symbols` array. Each entry in this array is a 3-item array, `[index_a, index_b, bond_order]`, where the indices correspond to the atom indices in `symbols`.
extras	dict	N/A	Extra information to associate with this molecule.
fix_symmetry	str	`g_rot`	Maximal point group symmetry with which the molecule should be treated.
fragments	list(N_fr)	N/A	An array that designates which sets of atoms are fragments within the molecule. This is a nested array, with the indices of the base array corresponding to the values in `fragment_charges` and `fragment_multiplicities` and the values in the nested arrays corresponding to the indices of `symbols`.
fragment_charges	list(N_fr)	N/A	The total charge of each fragment in `fragments`. The indices of this array correspond to the `fragments` ordering.
fragment_multiplicities	list(N_fr)	N/A	The multiplicity of each fragment in `fragments`. The indices of this array correspond to the `fragments` ordering.
id	str	N/A	A unique identifier for this molecule.
identifiers	dict	N/A	Additional identifiers by which this molecule can be referenced, such as INCHI, SMILES, etc.
real	list(N_at)	`atcorenums`	An array indicating whether each atom is real (true) or a ghost/virtual atom (false). The indices of this array correspond to the `symbols` ordering.
mass_numbers	list(N_at)	`atmasses`	An array of atomic mass numbers for each atom. The indices of this array correspond to the `symbols` ordering.
masses	list(N_at)	`atmasses`	An array of atomic masses [u] for each atom. Typically inferred from `symbols`. The indices of this array correspond to the `symbols` ordering.
name	str	`title`	An arbitrary, common, or human-readable name to assign to this molecule.

Note: N_at corresponds to the number of atoms in the molecule, as defined by the length of symbols; N_fr corresponds to the number of fragments in the molecule, as defined by the length of fragments. Fragment data is stored in a sub-dictionary, fragments.

The following are additional optional keywords used in QCElemental’s QCSchema implementation. These keywords mostly correspond to specific QCElemental functionality, and may not necessarily produce similar results in other QCSchema parsers.

Field	Type	Description
fix_com	bool	An indicator to prevent pre-processing the molecule by translating the COM to (0,0,0) in Euclidean coordinate space.
fix_orientation	bool	An indicator to prevent pre-processing the molecule by orienting via the inertia tensor.
validated	bool	An indicator that the input molecule data has been previously checked for schema and physics (e.g. non-overlapping atoms, feasible multiplicity) compliance. Generally should only be true when set by a trusted validator.

Input Schema¶

The qcschema_input subschema describes all data necessary to generate and parse a QC program input file for a given molecule.

The following is an example of a minimal qcschema_input file:

{
  "schema_name": "qcschema_input",
  "schema_version": 2.0,
  "molecule": {
    "schema_name": "qcschema_molecule",
    "schema_version": 2.0,
    "symbols":  ["Li", "Cl"],
    "geometry": [0.000000, 0.000000, -1.631761, 0.000000, 0.000000, 0.287958],
    "molecular_charge": 0.0,
    "molecular_multiplicity": 1,
    "provenance": {
      "creator": "HORTON3",
      "routine": "Manual validation"
    }
  },
  "driver": "energy",
  "model": {
    "method": "B3LYP",
    "basis": "Def2TZVP"
  }
}

The required fields and corresponding types for a qcschema_input file are:

Field	Type	IOData attr.	Description
schema_name	str	N/A	The QCSchema specification to which this model conforms. Fixed as `qcschema_input`.
schema_version	float	N/A	The version number of `schema_name` to which this model conforms, currently 2.
molecule	dict	N/A	QCSchema Molecule instance.
driver	str	N/A	The type of calculation being performed. One of `energy`, `gradient`, `hessian`, or `properties`.
model	dict	N/A	The quantum chemistry model specification for a given operation to compute against. See Model section below.

The optional fields and corresponding types for a qcschema_input file are:

Field	Type	IOData attr.	Description
extras	dict	N/A	Extra information associated with the input.
id	str	N/A	An identifier for the input object.
keywords	dict	N/A	QC program-specific keywords to be used for a computation. See details below for IOData-specific usages.
protocols	dict	N/A	Protocols regarding the manipulation of the output that results from this input. See Protocols section below.
provenance	dict or list	N/A	Information about the file was generated, provided, and manipulated. See Provenance section above for more information.

IOData currently supports the following keywords for qcschema_input files:

Keyword	Type	IOData attr.	Description
run_type	str	`run_type`	The type of calculation that lead to the results stored in IOData, which must be one of the following: `energy`, `energy_force`, `opt`, `scan`, `freq` or None.

Model Subschema¶

The model dict contains the following fields:

Field	Type	IOData attr.	Description
method	str	`lot`	The level of theory used for the computation (e.g. B3LYP, PBE, CCSD(T), etc.)
basis	str or dict	N/A	The quantum chemistry basis set to evaluate (e.g. 6-31G, cc-pVDZ, etc.) Can be ‘none’ for methods without basis sets. Must be either a string specifying the basis set name (the same as its name in the Basis Set Exchange, when possible) or a qcschema_basis instance.

Protocols Subschema¶

The protocols dict contains the following fields:

Field	Type	IOData attr.	Description
wavefunction	str	N/A	Specification of the wavefunction properties to keep from the resulting output. One of `all`, `orbitals_and_eigenvalues`, `return_results`, or `none`.
keep_stdout	bool	N/A	An indicator to keep the output file from the resulting output.

Output Schema¶

The qcschema_output subschema describes all data necessary to generate and parse a QC program’s output file for a given molecule.

The following is an example of a minimal qcschema_output file:

{
  "schema_name": "qcschema_output",
  "schema_version": 2.0,
  "molecule": {
    "schema_name": "qcschema_molecule",
    "schema_version": 2.0,
    "symbols":  ["Li", "Cl"],
    "geometry": [0.000000, 0.000000, -1.631761, 0.000000, 0.000000, 0.287958],
    "molecular_charge": 0.0,
    "molecular_multiplicity": 1,
    "provenance": {
      "creator": "HORTON3",
      "routine": "Manual validation"
    }
  },
  "driver": "energy",
  "model": {
    "method": "HF",
    "basis": "STO-4G"
  },
  "properties": {},
  "return_result": -464.626219879,
  "success": true
}

The required fields and corresponding types for a qcschema_output file are:

Field	Type	IOData attr.	Description
schema_name	str	N/A	The QCSchema specification to which this model conforms. Fixed as `qcschema_output`.
schema_version	float	N/A	The version number of `schema_name` to which this model conforms, currently 2.
molecule	dict	N/A	QCSchema Molecule instance.
driver	str	N/A	The type of calculation being performed. One of `energy`, `gradient`, `hessian`, or `properties`.
model	dict	N/A	The quantum chemistry model specification for a given operation to compute against.
properties	dict	N/A	Named properties of quantum chemistry computations. See Properties section below.
return_result	varies	N/A	The result requested by the `driver`. The type depends on the `driver`.
success	bool	N/A	An indicator for the success of the QC program’s execution.

The optional fields and corresponding types for a qcschema_output file are:

Field	Type	IOData attr.	Description
error	dict	N/A	A complete description of an error-terminated computation. See Error section below.
extras	dict	N/A	Extra information associated with the input. Also specified for qcschema_input.
id	str	N/A	An identifier for the input object. Also specified for qcschema_input.
keywords	dict	N/A	QC program-specific keywords to be used for a computation. See details below for IOData-specific usages. Also specified for qcschema_input.
protocols	dict	N/A	Protocols regarding the manipulation of the output that results from this input. See Protocols section above. Also specified for qcschema_input.
provenance	dict or list	N/A	Information about the file was generated, provided, and manipulated. See Provenance section above for more information. Also specified for qcschema_input.
stderr	str	N/A	The standard error (stderr) of the associated computation.
stdout	str	N/A	The standard output (stdout) of the associated computation.
wavefunction	dict	N/A	The wavefunction properties of a QC computation. All matrices appear in column-major order. See Wavefunction section below.

Properties Subschema¶

The properties dict contains named properties of quantum chemistry computations. Due to the variability possible for the contents of an output file, IOData does not guess at which properties are desired by the user, and stores all properties in the extra["output]["properties"] dict for easy retrieval. The current QCSchema standard provides names for the following properties:

Field	Description
calcinfo_nbasis	The number of basis functions for the computation.
calcinfo_nmo	The number of molecular orbitals for the computation.
calcinfo_nalpha	The number of alpha electrons in the computation.
calcinfo_nbeta	The number of beta electrons in the computation.
calcinfo_natom	The number of atoms in the computation.
nuclear_repulsion_energy	The nuclear repulsion energy term.
return_energy	The energy of the requested method, identical to `return_value` for energy computations.
scf_one_electron_energy	The one-electron (core Hamiltonian) energy contribution to the total SCF energy.
scf_two_electron_energy	The two-electron energy contribution to the total SCF energy.
scf_vv10_energy	The VV10 functional energy contribution to the total SCF energy.
scf_xc_energy	The functional (XC) energy contribution to the total SCF energy.
scf_dispersion_correction_energy	The dispersion correction appended to an underlying functional when a DFT-D method is requested.
scf_dipole_moment	The X, Y, and Z dipole components.
scf_total_energy	The total electronic energy of the SCF stage of the calculation.
scf_iterations	The number of SCF iterations taken before convergence.
mp2_same_spin_correlation_energy	The portion of MP2 doubles correlation energy from same-spin (i.e. triplet) correlations.
mp2_opposite_spin_correlation_energy	The portion of MP2 doubles correlation energy from opposite-spin (i.e. singlet) correlations.
mp2_singles_energy	The singles portion of the MP2 correlation energy. Zero except in ROHF.
mp2_doubles_energy	The doubles portion of the MP2 correlation energy including same-spin and opposite-spin correlations.
mp2_total_correlation_energy	The MP2 correlation energy.
mp2_correlation_energy	The MP2 correlation energy.
mp2_total_energy	The total MP2 energy (MP2 correlation energy + HF energy).
mp2_dipole_moment	The MP2 X, Y, and Z dipole components.
ccsd_same_spin_correlation_energy	The portion of CCSD doubles correlation energy from same-spin (i.e. triplet) correlations.
ccsd_opposite_spin_correlation_energy	The portion of CCSD doubles correlation energy from opposite-spin (i.e. singlet) correlations
ccsd_singles_energy	The singles portion of the CCSD correlation energy. Zero except in ROHF.
ccsd_doubles_energy	The doubles portion of the CCSD correlation energy including same-spin and opposite-spin correlations.
ccsd_correlation_energy	The CCSD correlation energy.
ccsd_total_energy	The total CCSD energy (CCSD correlation energy + HF energy).
ccsd_dipole_moment	The CCSD X, Y, and Z dipole components.
ccsd_iterations	The number of CCSD iterations taken before convergence.
ccsd_prt_pr_correlation_energy	The CCSD(T) correlation energy.
ccsd_prt_pr_total_energy	The total CCSD(T) energy (CCSD(T) correlation energy + HF energy).
ccsd_prt_pr_dipole_moment	The CCSD(T) X, Y, and Z dipole components.
ccsd_prt_pr_iterations	The number of CCSD(T) iterations taken before convergence.
ccsdt_correlation_energy	The CCSDT correlation energy.
ccsdt_total_energy	The total CCSDT energy (CCSDT correlation energy + HF energy).
ccsdt_dipole_moment	The CCSDT X, Y, and Z dipole components.
ccsdt_iterations	The number of CCSDT iterations taken before convergence.
ccsdtq_correlation_energy	The CCSDTQ correlation energy.
ccsdtq_total_energy	The total CCSDTQ energy (CCSDTQ correlation energy + HF energy).
ccsdtq_dipole_moment	The CCSDTQ X, Y, and Z dipole components.
ccsdtq_iterations	The number of CCSDTQ iterations taken before convergence.

Error Subschema¶

The error dict contains the following fields:

Field	Type	IOData attr.	Description
error_type	str	N/A	The type of error raised during the computation.
error_message	str	N/A	Additional information related to the error, such as the backtrace.
extras	dict	N/A	Additional data associated with the error.

Wavefunction subschema¶

The wavefunction subschema contains the wavefunction properties of a QC computation. All matrices appear in column-major order. The current QCSchema standard provides names for the following wavefunction properties:

Field	Description
basis	A `qcschema_basis` instance for the one-electron AO basis set. AO basis functions are ordered according to the CCA standard as implemented in libint.
restricted	An indicator for a restricted calculation (alpha == beta). When true, all beta quantites are omitted, since quantity_b == quantity_a
h_core_a	Alpha-spin core (one-electron) Hamiltonian.
h_core_b	Beta-spin core (one-electron) Hamiltonian.
h_effective_a	Alpha-spin effective core (one-electron) Hamiltonian.
h_effective_b	Beta-spin effective core (one-electron) Hamiltonian.
scf_orbitals_a	Alpha-spin SCF orbitals.
scf_orbitals_b	Beta-spin SCF orbitals.
scf_density_a	Alpha-spin SCF density matrix.
scf_density_b	Beta-spin SCF density matrix.
scf_fock_a	Alpha-spin SCF Fock matrix.
scf_fock_b	Beta-spin SCF Fock matrix.
scf_eigenvalues_a	Alpha-spin SCF eigenvalues.
scf_eigenvalues_b	Beta-spin SCF eigenvalues.
scf_occupations_a	Alpha-spin SCF orbital occupations.
scf_occupations_b	Beta-spin SCF orbital occupations.
orbitals_a	Keyword for the primary return alpha-spin orbitals.
orbitals_b	Keyword for the primary return beta-spin orbitals.
density_a	Keyword for the primary return alpha-spin density.
density_b	Keyword for the primary return beta-spin density.
fock_a	Keyword for the primary return alpha-spin Fock matrix.
fock_b	Keyword for the primary return beta-spin Fock matrix.
eigenvalues_a	Keyword for the primary return alpha-spin eigenvalues.
eigenvalues_b	Keyword for the primary return beta-spin eigenvalues.
occupations_a	Keyword for the primary return alpha-spin orbital occupations.
occupations_b	Keyword for the primary return beta-spin orbital occupations.

dump_one(f, data)[source]¶

Dump a single frame into a QCSchema file.

Parameters:

f (TextIO) – A writeable file object.
data (IOData) – An IOData instance which must have the following attributes initialized: atnums, atcoords, charge, spinpol. If the following attributes are present, they are also dumped into the file: title, atcorenums, atmasses, bonds, g_rot, extra.

Notes

load_one(lit)[source]¶

Load a single frame from a QCSchema file.

Parameters:: lit (LineIterator) – The line iterator to read the data from.
Return type:: dict
Returns:: result (dict) – A dictionary with IOData attributes. The following attributes are guaranteed to be loaded: atnums, atcorenums, atcoords, charge, nelec, spinpol. The following may be loaded if present in the file: atmasses, bonds, energy, g_rot, lot, obasis, obasis_name, title, extra.

prepare_dump(data, allow_changes, filename)[source]¶

Check the compatibility of the IOData object with QCScheme.

Parameters:

data (IOData) – The IOData instance to be checked.
allow_changes (bool) – Whether conversion of the IOData object to a compatible form is allowed or not. (not relevant for QCSchema JSON, present for API consistency)
filename (str) – The file to be written to, only used for error messages.

Return type:

IOData

Returns:

data – The given IOData object.

Raises:

PrepareDumpError – If the given IOData instance is not compatible with the WFN format.