Formats, units, and exports
Find the formats openWFN can read and write, and the units used in results.
Run openwfn FILE capabilities to see what your particular file supports.
Registered input suffixes
The parser registry accepts these filename suffixes. Files without a suffix may still be recognized as single-frame XYZ when their contents match that format.
| Suffix | Parsed content |
|---|---|
.chk |
Gaussian binary checkpoint via the external formchk utility |
.cub |
Gaussian volumetric grid |
.cube |
Gaussian volumetric grid |
.fch |
Gaussian formatted checkpoint |
.fchk |
Gaussian formatted checkpoint with native wavefunction records |
.log |
Gaussian calculation metadata |
.mol |
V2000 molecular structure |
.out |
Gaussian calculation metadata |
.pdb |
Molecular structure and available connectivity |
.sdf |
V2000 molecular structure |
.xyz |
Single-frame molecular structure |
doctor uses the canonical loader across these input kinds. summary returns
a partial structure record when geometry exists but a full wavefunction does
not. Electronic analyses fail cleanly when required records are absent.
Element symbols can still provide a formula and atom count when effective
nuclear charges are missing. Explicit ghost centers are excluded. In that case,
the formula describes the reported element composition; physical-nucleus and
ghost/ECP classification remain unconfirmed and are not inferred from symbols.
Stable interoperability formats
Molden detection accepts .molden.input and recognizes
the [Molden Format] header for unrecognized filenames. Structure exports warn
when molecular charge or spin multiplicity cannot be retained, in addition to
ghost/ECP warnings. Keep the original calculation and its metadata; reloading a
structure export is not an electronic-state round-trip.
openWFN includes the IOData reader in its base installation. This is the pinned IOData 1.0.1
readable-format inventory. “Stable” means ingestion passed
the project fixture contract; it does not mean every analysis is available,
or that all real-world variants have been independently validated. Native
FCHK remains the preferred path for Gaussian formatted checkpoints. The
“components” column describes the pinned fixture, not a promise about every
file in that format. calculation can be structure-only and does not imply
that orbitals or a basis are present.
| Format ID | Typical filename | Preferred path | Fixture components | Ingestion status |
|---|---|---|---|---|
charmm |
.crd, .psf |
IOData | metadata, structure | Stable |
chgcar |
CHGCAR, CHGCAR-*, .chgcar |
IOData | grids, metadata, periodic, structure | Stable |
cp2klog |
CP2K .out |
IOData; detected from content | calculation, metadata, structure | Stable |
cube |
.cube, .cub |
Native | grids | Stable |
extxyz |
.extxyz |
IOData | metadata, structure | Stable |
fchk |
.fchk, .fch |
Native | calculation, metadata, structure | Stable |
fcidump |
FCIDUMP, .fcidump |
IOData | integrals | Stable |
gamess |
GAMESS .dat or .out |
IOData; explicit hint may be needed | metadata, structure | Stable |
gaussianinput |
.gjf, .com |
IOData | metadata, structure | Stable |
gaussianlog |
Gaussian .log |
Native by default; IOData with explicit hint | metadata | Stable |
gromacs |
.gro |
IOData | metadata, periodic, structure | Stable |
json_qcschema |
.qcschema.json |
IOData | metadata, structure | Stable |
locpot |
LOCPOT, LOCPOT-*, .locpot |
IOData | grids, metadata, periodic, structure | Stable |
mol2 |
.mol2 |
IOData | metadata, structure | Stable |
molden |
.molden |
IOData | calculation, metadata, structure | Stable |
molekel |
.mkl |
IOData | calculation, structure | Stable |
mwfn |
.mwfn |
IOData | calculation, metadata, structure | Stable |
orcalog |
ORCA .out |
IOData; detected from content | metadata, structure | Stable |
pdb |
.pdb |
Native | calculation, metadata, structure | Stable |
poscar |
POSCAR, POSCAR-*, .poscar, .vasp |
IOData | metadata, periodic, structure | Stable |
qchemlog |
Q-Chem .out |
IOData; detected from content | metadata, structure | Stable |
sdf |
.sdf, .mol |
Native | calculation, metadata, structure | Stable |
wfn |
.wfn |
IOData | calculation, metadata, structure | Stable |
wfx |
.wfx |
IOData | calculation, metadata, structure | Stable |
xyz |
.xyz |
Native | calculation, metadata, structure | Stable |
The 25 fixture contracts and cross-format numerical checks are recorded in
validation/interop.
The five water wavefunction representations share one originating calculation;
their agreement is a cross-format regression, not independent experimental
confirmation. WFN/WFX expose 21 primitive functions where the contracted
FCHK/Molden/MWFN representations expose 13 basis functions.
Structure outputs
convert writes XYZ, PDB, MOL, or SDF. These formats primarily carry structure and connectivity; they do not preserve the full wavefunction. The legacy xyz command writes atom symbols and Cartesian coordinates.
When a source contains ghost or ECP effective nuclear charges, these outputs
warn that the charges cannot survive the conversion. The direct Python
write_structure function returns the same warning strings. Cube headers
retain effective nuclear charges.
openwfn molecule.molden convert --to sdf --output molecule.sdf
openwfn molecule.molden xyz molecule.xyz
Scientific outputs
Read results as terminal text, JSON or CSV. JSON keeps the complete result,
including units, source information, warnings and diagnostics. export saves
frontier-orbital or population tables. plot frontier makes a figure from the
result, and density cube saves a volumetric field in cube format.
Keep JSON beside CSV curves when you need complete units, settings, warnings and source information. CSV is a tabular view, not the complete result record. Frontier and general population table exports include result status, warnings and provenance columns. A failed analysis can be saved as an error record in JSON, but not as an empty scientific CSV table. Table and spectrum exports are published only after writing finishes; a failed write leaves an existing output unchanged. HTML reports embed complete result records, including failed analyses.
Batch runs write detailed JSON result records plus batch-summary.csv, a compact
index suitable for spreadsheets and dataframe ingestion.
HTML outputs
report build, workbench, and view can create self-contained HTML. Reports are
supported research records when preserved with their machine-readable results. The
workbench is an optional visualization surface with a Stable interface for the tested Chromium scope, not a numerical reference.
“Self-contained” means no openWFN server is required; it does not mean the artifact is
free of research data.
The viewer and workbench embed 3Dmol.js, licensed under BSD-3-Clause, and retain that attribution in each generated file. They do not load the rendering library from a remote server.
Units
| Quantity | Presentation or control unit |
|---|---|
| Molecular coordinates and distances | ångström |
| Angles and dihedrals | degree |
| Wavefunction orbital and total energies | hartree; gaps also reported in eV |
| Source-output frontier energies and excitation energies | eV |
| Density-grid spacing and padding | bohr |
| CLI/high-level API ESP point coordinates | ångström |
| Electrostatic potential | hartree/e |
| Density-derivative, ELF/LOL/NCI and QTAIM coordinates | bohr |
Always follow the label in machine-readable output and the installed version's help. See scientific methods for definitions.