orca-step 2026.6.28

A SEAMM plug-in for ORCA

SEAMM ORCA Plug-in

A SEAMM plug-in for ORCA

• Free software: BSD-3-Clause

• Documentation: https://molssi-seamm.github.io/orca_step/index.html

• Code: https://github.com/molssi-seamm/orca_step

Features

A SEAMM plug-in for ORCA, a general-purpose quantum-chemistry program, with an emphasis on accurate molecular calculations such as DLPNO-CCSD(T).

Like the MOPAC and Gaussian steps, the ORCA step is a sub-flowchart: you add an ORCA node to your flowchart and then build a small sub-flowchart of ORCA capabilities inside it. Initially the available capabilities are:

• Energy – a single-point energy.

• Optimization – a geometry optimization.

Further capabilities (frequencies, properties, …) will be added.

Methods are described by the step’s metadata and can be set either explicitly in the ORCA dialog (similar to the Gaussian step) or, by default, taken from a preceding Model Chemistry step. Basis sets default to ORCA’s built-in families (Pople, Dunning cc, and Karlsruhe def2), with the Basis Set Exchange available as a planned opt-in source.

Acknowledgements

This package was created with the molssi-seamm/cookiecutter-seamm-plugin tool, which is based on the excellent Cookiecutter.

Developed by the Molecular Sciences Software Institute (MolSSI), which receives funding from the National Science Foundation under award CHE-2136142.

History

2026.6.28 – Properties, gradients, citations, and wavefunction export

• Reports many properties from a single calculation: HOMO/LUMO (and the next orbitals) and the gap, the dipole moment, rotational constants, <S^2>, the Mulliken, Löwdin, and Hirshfeld atomic charges, the Mayer bond orders and valences, and the optional dipole polarizability.

• The Mayer bond orders and Hirshfeld charges can be written to a CSV file and applied to the structure.

• Energy gradients can be requested and are written to Results.json for use by driver steps such as Thermochemistry and Reaction Path.

• Full citations for each run: the ORCA program, the DFT functional (from the ORCA manual), the basis set (via the Basis Set Exchange), and the supporting integral and exchange-correlation libraries.

• Basis sets can be taken from the Basis Set Exchange, including a ‘bse:NAME’ shorthand that forces a single basis from the Exchange.

• Can write an analytic wavefunction (.wfx, via orca_2aim) for a following Atomic Charges step to partition into DDEC6 charges.

• Fixed: the Results tab in the GUI was empty; it now lists the available results to save to variables, tables, or JSON.

2026.6.27 – Initial release of the ORCA step

• A sub-flowchart ORCA plug-in with Energy and Optimization sub-steps.

• Single-point energies and geometry optimizations, including DLPNO-CCSD(T).

• The method and basis set can be set explicitly, or taken from a preceding Model Chemistry step. Basis sets use ORCA’s built-in families.