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

SCINE autoCAS is a graphical user interface that implements an orbital entanglement based active orbital selection protocol by connection of the SCINE QCMaquis DMRG program and the OpenMolcas electronic structure program. The information that is gathered during the individual steps of the calculation is stored in a JSON-type data format and ensures transferability between different platforms. In this way, a calculation can be set up on a workstation or laptop, whereas the more expensive calculations can be carried out on a computing cluster. SCINE autoCAS offers a fully automated and a semiautomated mode, where each individual step of the calculation is monitored by the user.

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
  • 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


Important Note

An updated version with a new feature for the automated active space selection for very large valence spaces as described in this article will be available soon!

Future Releases

Important Note

An updated version with a new feature for the automated active space selection for very large valence spaces as described in this article will be available soon!

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
  • Automated active orbital selection along reaction coordinates
We are planning to release the source code of autoCAS in 2020.


See the manual for introductory examples, an overview of the functionality of SCINE autoCAS and a discussion of possible use cases.


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 in case of any questions and suggestions.


  • Primary reference:
    C. J. Stein, M. Reiher, "autoCAS: A Program for Fully Automated Multiconfigurational Calculations", J. Comp. Chem,, 2019, DOI: 10.1002/jcc.25869. 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