ORCA Input

Item	Value
Format ID	orcainp
Extensions	.inp
Read	Yes
Write	Yes
Registry role	Reader, file writer, frame writer
Data level	Coordinates and QM input semantics

ORCA input parsing with coordinates, multi-job splitting, model chemistry, task-family fixtures, and structured request containers.

Coordinate-bearing frames can be rendered with explicit ORCA calculation settings:

Download the shared ORCA example, then run:

Python

from molop import AutoParser

frame = AutoParser("water_mp2.out", n_jobs=1)[0][-1]
rendered = frame.format_transform(
    "orcainp",
    keywords="wB97M-V def2-TZVPP RIJCOSX def2/J TightSCF DefGrid3 NoAutoStart SP",
    nprocs=16,
    maxcore=4000,
    blocks={"scf": {"MaxIter": 300, "STABPerform": True}},
)

rendered is a string containing the ORCA simple input line, %pal/%maxcore/%scf, and an * xyz coordinate block.

Output

Text Only

! wB97M-V def2-TZVPP RIJCOSX def2/J TightSCF DefGrid3 NoAutoStart SP

%pal
  nprocs 16
end

%maxcore 4000

%scf
  MaxIter 300
  STABPerform true
end

* xyz 0 1
O      1.7849140000     1.2624220000     0.5119850000
H      2.6482370000     1.0729290000     0.1316310000
H      1.1831680000     1.2568160000    -0.2388350000
*

Cross-format conversion requires keywords; MolOP does not reuse keyword syntax from another QM program. Raw %block text is also accepted through blocks.

Feature	Support	Scope	Limits
Geometry and job splitting	Partial	Direct coordinates, point charges, external xyzfile/pdbfile references, and $new_job splitting.	External geometry references are parsed as references; parser does not require dereferencing external files.
Model chemistry and options	Partial	Method, functional, basis, auxiliary basis, dispersion-as-functional-suffix, mixed basis, print settings, PARAS variables, and scan coordinates.	Unsupported ORCA block options may remain raw/resource fields instead of dedicated semantic containers.
ORCA 6 manual fixture families	Fixture-covered	Single point, SCF stability, optimization, frequency, excited-state, MRCI, and Solvator input examples.	Manual snippets without complete explicit geometry are intentionally excluded from fixture coverage.
Excited-state and multireference requests	Partial	Structured excited-state and multireference task semantics, including MRCI multi-job fixtures.	ORCA excited-state and multireference keyword families outside the covered examples may still be raw.
Optimization, coordinates, frequency, and Solvator structures	Partial	Optimization constraints, internal coordinates, fragments, NEB, frequency restart, and Solvator examples.	Coverage follows explicit ORCA manual fixtures and targeted regression examples.
Writer availability	Partial	Canonical file/frame rendering from coordinate-bearing models with explicit keywords, PAL, maxcore, arbitrary percent blocks, Cartesian geometry, and .inp output paths.	Non-Cartesian inline geometry and arbitrary source-statement ordering are not canonicalized; cross-format conversion requires explicit ORCA keywords.

ORCA 6.1 Capability Matrix

The matrix distinguishes four levels so that raw-text retention is not mistaken for structured support:

• Supported: the listed syntax has an explicit model and tests for reading or canonical rendering.
• Partial: only known forms or fixtures are covered; all ORCA 6.1 variants are not guaranteed.
• Raw: original %block text can be passed through, but MolOP does not interpret or validate it.
• Unsupported: the input is rejected, information is lost, or the model cannot regenerate it.

ORCA input capability	Parse	Structured semantics	Canonical render	Source fidelity	Current boundary
! simple keyword lines	Supported	Partial	Supported	Unsupported	Keyword text is retained; method, functional, and basis recognition uses built-in vocabularies, and output is reformatted.
Top-level # comments	Partial	Not applicable	Supported	Unsupported	Standalone comment lines are stored; global position is lost, and parsing does not resume after a closing # on the same line.
%maxcore and %pal	Supported	Supported	Supported	Partial	Structured maxcore and nprocs overrides are supported; output uses canonical formatting.
Ordinary non-nested %block ... end	Supported	Partial	Raw	Partial	Unmodeled blocks can remain in ORCABlock.raw_text, but their original position relative to other statement types is not guaranteed.
Single-line % directives such as %moinp and %base	Partial	Unsupported	Raw	Partial	Generic block scanning captures them; most have no dedicated model or parameter validation beyond resource fields.
Nested blocks such as %scf/SOSCF and %basis/NewGTO	Partial	Partial	Partial	Unsupported	Nested recognition uses a limited allowlist; an unknown inner end can truncate the outer block.
Repeated blocks and input priority	Partial	Unsupported	Partial	Unsupported	Parsing keeps block-list order; name-based override removes old instances and appends the replacement at the end.
Unclassified top-level statements	Partial	Unsupported	Partial	Unsupported	They are stored in trailing_lines and rendered after geometry.
* xyz, * cart, and * cartesian	Supported	Supported	Supported	Unsupported	Coordinates are canonicalized as * xyz; whitespace, significant digits, and the original coordinate type are not retained.
Cartesian geometry in %coords	Supported	Supported	Supported	Unsupported	Parsed geometry is rendered as * xyz, not regenerated as %coords.
Point charges Q q x y z	Supported	Supported	Supported	Unsupported	Charges use six decimal places; coordinates use the writer precision setting.
Ghost, dummy, fragment, frozen, and atom-level basis markers	Partial	Partial	Partial	Unsupported	Covered fixture forms are handled; original tokens, quoting, and ordering are not guaranteed.
Isotope M= and nuclear charge Z=	Supported	Supported	Unsupported	Unsupported	The parser stores both atom attributes, but the Cartesian writer does not emit them.
* int, * internal, and * gzmt	Partial	Partial	Unsupported	Unsupported	Covered numeric internal coordinates can be parsed and projected to Cartesian coordinates; rendering raises NotImplementedError.
* xyzfile, * gzmtfile, and * pdbfile	Supported	Supported	Supported	Partial	The path reference is stored and rendered without reading or validating the external file.
%paras and coordinate expressions	Partial	Partial	Partial	Unsupported	Simple parameters, ranges, and name +/- offset are recognized; geometry rendering replaces expressions with resolved values.
$new_job multi-job input	Supported	Supported	Supported	Unsupported	Each job maps to one frame; output uses a canonical $new_job separator.
%Compound workflows	Partial	Unsupported	Unsupported	Unsupported	Valid Compound-only input without top-level geometry is rejected by format probing; rendering also requires keywords and geometry.
Model chemistry and common tasks	Partial	Partial	Partial	Not applicable	Common SP, OPT, TS/NEB, FREQ, IRC, gradient, DFT, selected wavefunction methods, and dispersion keywords are covered.
Excited-state, multireference, and Solvator input	Partial	Partial	Raw	Partial	Parsing provides structured requests; rendering relies on retained raw blocks or explicit blocks and does not fully synthesize blocks from request models.
Full %basis, ECP, AuxJ/AuxJK/AuxC/CABS	Partial	Unsupported	Raw	Partial	Simple keywords and atom-level overrides are recognized; complete block contents are not modeled or validated field by field.
ORCA 6.1 QMMM, MD, GOAT, DOCKER, RESP, Raman, and similar features	Partial	Unsupported	Raw	Partial	Non-nested raw blocks can be supplied; nested syntax, task compatibility, and field-level construction are not guaranteed.
ORCA version and compatibility validation	Unsupported	Unsupported	Unsupported	Not applicable	The version is currently recorded as Any; keyword, method, basis, and ORCA-version compatibility are not checked.

The current renderer is a canonical writer for constructing new input from coordinates and explicit calculation settings. It is not a source-preserving writer. Do not rely on round-trip behavior when editing one field in an existing complex input must leave all other source text unchanged.

References: ORCA 6.1 input structure, coordinates, basis sets, and Compound.