Keywords · ORCA User Guide

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Run types
Hartree–Fock · DFT methods
Correlated methods — MP2, CCSD(T), DLPNO
SCF algorithm options
SCF · optimisation convergence thresholds
DFT integration grids
Relativistic options
Output control
Composite methods

This page is a condensed reorganisation of the keyword tables in section 4.2 of the ORCA manual. The full list runs to over a thousand pages, so this sticks to the keywords that show up most often in everyday research. For anything missing, section 4.2 of the manual has the complete set.

Run types

If no run type is specified on the keyword line, the default is Energy (single point).

Keyword	Meaning
`Energy` or `SP`	Single-point energy (default).
`Opt`	Geometry optimisation (uses the redundant internal coordinates introduced in 2022).
`COpt`	Optimisation in Cartesian coordinates.
`OptTS`	Transition-state optimisation.
`ScanTS`	Relaxed scan followed by a TS search.
`NEB`, `NEB-CI`, `NEB-TS`	Nudged Elastic Band methods.
`IRC`	Intrinsic Reaction Coordinate tracing.
`Freq` or `AnFreq`	Analytical frequency calculation.
`NumFreq`	Numerical frequency calculation.
`EnGrad`	Energy + gradient only (writes extra files beyond the GBW).
`NumGrad`	Numerical gradient (when analytical derivatives are unavailable).
`MD`	Molecular dynamics.
`GOAT`	Global geometry optimisation + conformer search (ORCA 6).

Hartree–Fock · DFT methods

Hartree–Fock

HF itself is a one-word keyword. You can specify closed- vs open-shell explicitly.

Keyword	Meaning
`HF`	Hartree–Fock.
`RHF` / `RKS`	Restricted (closed-shell) SCF.
`UHF` / `UKS`	Unrestricted SCF.
`ROHF` / `ROKS`	Restricted open-shell SCF.

Representative DFT functionals

The functionals below are the ones you will meet most often. A fuller list is covered in 12. DFT functionals.

Family	Keyword	Description
GGA	`BP86` · `BP`	Becke88 exchange + Perdew86 correlation. Popular for transition metals.
	`BLYP`	Becke88 + Lee–Yang–Parr.
	`PBE`	Perdew–Burke–Ernzerhof. Solid general-purpose choice.
Hybrid GGA	`B3LYP`	20 % HF exchange. The most widely used reference.
	`B3LYP/G`	Gaussian-style variant (VWN3 instead of VWN5).
	`PBE0`	25 % HF exchange. Strong for NMR and EPR.
	`BHANDHLYP`	50 % HF exchange.
meta-GGA	`TPSS`	Representative meta-GGA.
	`TPSSh`	10 % HF-exchange hybrid.
	`M06L`	Truhlar group's meta-GGA.
Hybrid meta-GGA	`M06`	27 % HF exchange.
	`M062X`	54 % HF exchange. Good for reaction barriers.
	`r2SCANh` · `r2SCAN0`	r²SCAN-based hybrids. Modern recommendation.
Range-separated	`CAM-B3LYP`	Good for excited states and charge transfer.
	`wB97X-V`	Includes VV10 non-local correlation.
	`wB97M-V`	meta-GGA + VV10. Among the best overall performers.
Double hybrid	`B2PLYP`	B88 + LYP + MP2 mix. High accuracy.
Double hybrid	`DSD-PBEP86`	SCS-MP2-coupled double hybrid.

Dispersion corrections

DFT does not capture dispersion well, so it is best to add a dispersion correction in almost every case.

Keyword	Meaning
`D4`	Most recent D4 correction. The recommended choice in ORCA 6.
`D3BJ`	Grimme's D3 + Becke–Johnson damping. Very robust.
`D3ZERO`	D3 + zero damping.
`D2`	Older version — not recommended.

# Using B3LYP with a dispersion correction is essentially standard
! B3LYP D4 def2-TZVP

Correlated methods — MP2, CCSD(T), DLPNO

Keyword	Meaning
`MP2`	Standard MP2.
`RI-MP2` or `MP2RI`	MP2 with the RI approximation. Requires an auxiliary basis.
`SCS-MP2`	Spin-Component Scaled MP2. Improved accuracy.
`DLPNO-MP2`	Local PNO-based MP2. Designed for large molecules.
`CCSD`	Coupled Cluster Singles & Doubles.
`CCSD(T)`	Adds perturbative triples — the gold standard.
`DLPNO-CCSD`	Local PNO-based CCSD (closed-shell).
`DLPNO-CCSD(T)`	Local PNO-based CCSD(T). Full discussion in Chapter 10.
`F12-CCSD(T)` · `CCSD(T)-F12`	Includes F12 explicit correlation. Approaches the basis-set limit rapidly.

DLPNO thresholds

The precision of a DLPNO calculation is controlled through three levels:

Keyword	Description
`LoosePNO`	Fastest, lowest precision. Useful for exploration.
`NormalPNO`	The default. A balanced choice.
`TightPNO`	For benchmark / production accuracy. Roughly 2× slower.

SCF algorithm options

Keyword	Meaning
`RIJCOSX`	RI for Coulomb + Chain-of-Spheres exchange. The standard acceleration option for hybrid DFT.
`RI-JK`	Apply RI to both Coulomb and Exchange. Requires a JK auxiliary basis.
`RI`	Automatically active for pure GGAs. Uses Split-RI-J.
`NORI`	Disable RI.
`DIRECT`	Direct calculation of integrals (saves memory).
`CONV`	Store integrals on disk (I/O cost; required by some follow-up tasks).
`DIIS` · `NODIIS`	Enable / disable DIIS acceleration.
`SOSCF`	Second-order SCF. Often effective for closed-shell organics.
`TRAH`	Trust-Region Augmented Hessian SCF. The last resort for hard cases.
`MOREAD`	Read molecular orbitals from a previous calculation. Use with `%moinp "file.gbw"`.
`NOITER`	No SCF iterations — stop with the supplied orbitals.
`UNO`	Generate UHF natural orbitals. Recommended for unrestricted calculations.

SCF · optimisation convergence thresholds

Keyword	Description
`LooseSCF`	Loose SCF convergence — fast but imprecise.
`NormalSCF`	Default.
`TightSCF`	Recommended for optimisations and frequencies.
`VeryTightSCF`	For precision energies, NMR, and other sensitive jobs.
`ExtremeSCF`	Benchmark only — very expensive.
`LooseOpt`	Loose optimisation convergence.
`NormalOpt`	Default optimisation convergence.
`TightOpt`	Tight optimisation — needed if you want clean frequencies afterwards.
`VeryTightOpt`	Very tight.

SCF convergence strategy

Keyword	Description
`EasyConv`	Assume convergence will not be a problem — fastest option.
`NormalConv`	The general case.
`SlowConv`	Recommended for difficult cases such as transition-metal complexes.
`VerySlowConv`	For pathological convergence problems.

DFT integration grids

The size of the DFT numerical-integration grid is set with the DefGridN keyword. The default is DefGrid2.

Keyword	Description
`DefGrid1`	Coarsest grid — fast but less accurate.
`DefGrid2`	Default. Sufficient for everyday work.
`DefGrid3`	Large bases or precision work.
`NoFinalGridX`	Disable the final grid for COSX. Not recommended.

Relativistic options

Used when treating heavy elements — 5d / 6d transition metals, lanthanides, actinides.

Keyword	Description
`ZORA`	Zero-Order Regular Approximation. Recommended for magnetic properties.
`DKH` or `DKH2`	Second-order Douglas–Kroll–Hess Hamiltonian. Recommended for electric properties.
`X2C`	Two-component transformation. The modern option.
`SOMF(1X)`	Spin–orbit coupling. Often paired with magnetic-property calculations.

Relativistic calculations must use a dedicated basis. For example, ! ZORA ZORA-def2-TZVP SARC/J pairs a ZORA-recontracted basis with the SARC auxiliary basis.

Output control

Keyword	Description
`NormalPrint`	Standard output (default).
`SmallPrint`	Condensed output.
`LargePrint`	Verbose output — for debugging.
`MiniPrint`	Minimal output.
`PrintMOs`	Print molecular-orbital coefficients.
`PrintBasis`	Print the basis set actually used.
`PrintGap`	Print the HOMO–LUMO gap each SCF iteration.
`XYZFile`	Write coordinates as `.xyz`.
`PDBFile`	Write coordinates as `.pdb`.
`NoPop`	Disable all population analyses.
`Mulliken`, `Loewdin`, `Mayer`	Enable the corresponding population analysis.
`NBO`	NBO analysis interface (requires GENNBO).

Composite methods

Composite methods bundle "functional + basis + corrections" into a single keyword. ORCA 6 strongly recommends the "3c" family from the Grimme group: a single line is enough — no separate basis line required.

Keyword	Description
`HF-3c`	HF-based. Extremely fast — useful for structure searches.
`B97-3c`	GGA + modified def2-mTZVP. Excellent for everyday optimisations.
`r2SCAN-3c`	meta-GGA + modified def2-mTZVPP. Best price/performance — strongly recommended.
`PBEh-3c`	Hybrid (42 % HF) + modified def2-mSVP.
`wB97X-3c`	Range-separated hybrid + valence double-zeta.

# r2SCAN-3c — basis and corrections all applied automatically
! r2SCAN-3c Opt Freq

* xyzfile 0 1 mol.xyz

Reach for r²SCAN-3c first

For medium-sized molecules (50–200 atoms) — geometry optimisations and frequencies — try r2SCAN-3c first. It reaches B3LYP/def2-TZVP-level accuracy in less than half the time. When you then need a more precise single-point energy on top, a workflow that adds DLPNO-CCSD(T)/cc-pVTZ on top of the r²SCAN-3c geometry works very well.

That is the keyword dictionary. From the next chapter on, worked examples show how these actually combine in real calculations.