# autoCAS: a program for fully automated multi-configurational calculations

## TL;DR

autoCAS is a user-friendly software tool that automates multi-configurational electronic structure calculations, including active space selection, making complex quantum chemistry computations more accessible and efficient.

## Contribution

autoCAS introduces an automated active space selection protocol integrated into a graphical interface, enabling black-box multi-configurational calculations for large molecules.

## Key findings

- Automated active space selection for complex molecules.
- Minimal input required for multi-configurational calculations.
- Extension for large valence orbital spaces.

## Abstract

We present our implementation autoCAS for fully automated multi-configurational calculations, which we also make available free of charge on our webpages. The graphical user interface of autoCAS connects a general electronic structure program with a density matrix renormalization group program to carry out our recently introduced automated active space selection protocol for multi-configurational calculations [J. Chem. Theory Comput., 2016, 12, 1760]. Next to this active space selection, autoCAS carries out several steps of multi-configurational calculations so that only a minimal input is required to start them, comparable to that of a standard Kohn-Sham density functional theory calculation, so that black-box multi-configurational calculations become feasible. Furthermore, we introduce a new extension to the selection algorithm that facilitates automated selections for molecules with large valence orbital spaces consisting of several hundred orbitals.