SCINE autoCAS

Philosophy of SCINE autoCAS

The setup of multi-configurational electronic structure calculations is hampered by the need to select active orbitals — a process which is typically based on experience and empirical rules. This selection introduces an ambiguity and renders these methods hard to apply for all but experienced experts. SCINE autoCAS replaces the manual selection of active orbitals by an automated scheme that rigorously exploits the entanglement information obtained from partially converged, but qualitatively correct multi-configurational wave functions optimized with the density matrix renormalization group (DMRG).

Technical Details

Since version 2.0.0, SCINE autoCAS is a command-line Python program that implements an orbital entanglement based active orbital selection protocol by connection of the SCINE QCMaquis DMRG program and the OpenMolcas electronic structure program. In the simplest case, autoCAS only requires molecular coordinates (as an XYZ file) to determine the active space. For more complex use cases, the input can also be supplied via a dedicated YAML input file. Furthermore, autoCAS provides an easy-to-use API with which its functionality can be directly integrated into other Python programs.

Current Features

  • Automated selection of active orbitals for ground and excited states
  • Interfaces our quantum-chemical DMRG program SCINE QCMaquis with the electronic structure program OpenMolcas
  • Interface to Serenity
  • Automated analysis of the orbital entanglement entropies that are calculated from an approximate wave function
  • Fully automated multi-configurational calculations
  • Evaluation of the Zs(1) multi-configurational diagnostic
  • Export of entanglement and threshold diagrams
  • Consistent active spaces along reaction coordinates by means of an orbital mapping

Download

SCINE autoCAS is distributed as an open source code. Visit our GitHub page to download it.

Future Releases

Further releases are planned for the following features:

  • Full support of localized molecular orbital bases (requires hdf5 support of OpenMolcas localized orbital files)
  • Automated setup of DMRG-NEVPT2 calculations

Documentation

Documentation is provided in the source code; you can also access it here

Support

Despite intense testing of the program, the large variety of possible use cases and personal preferences for multi-configurational calculations may pose limits to SCINE autoCAS or to its interaction with electronic structure programs. Therefore do not hesitate to contact the developers via autocas@phys.chem.ethz.ch in case of any questions and suggestions.

References

  • Primary reference for autoCAS 2.3.1:
    M. Bensberg, M. Mörchen, C. J. Stein, J. P. Unsleber, T. Weymuth, M. Reiher, "qcscine/autocas: Release 2.3.1 (Version 2.3.1)", Zenodo, 2024. DOI
  • Primary reference for autoCAS 1.0.0:
    C. J. Stein, M. Reiher, "autoCAS: A Program for Fully Automated Multiconfigurational Calculations", J. Comp. Chem., 2019, 40, 2216. DOI
  • Original presentation of the approach:
    C. J. Stein, M. Reiher, "Automated selection of active orbital spaces", J. Chem. Theory Comput., 2016, 12, 1760. DOI
  • Automated active space selection with multi-reference perturbation theory:
    C. J. Stein, V. von Burg, M. Reiher, "The delicate balance of static and dynamic electron correlation", J. Chem. Theory Comput., 2016, 12, 3764. DOI
  • Excited states and reaction paths:
    C. J. Stein, M. Reiher, "Automated identification of relevant frontier orbitals for chemical compounds and processes", Chimia, 2017, 71, 170. DOI
  • Multi-configurational diagnostic:
    C. J. Stein, M. Reiher, "Measuring multi-configurational character by orbital entanglement", Mol. Phys., 2017, 115, 2110. DOI