BAGEL: Brilliantly Advanced General Electronic-structure Library

TL;DR

BAGEL is a comprehensive quantum chemistry software package offering advanced electronic-structure methods, including relativistic and multireference theories, with efficient parallelization and novel implementation techniques.

Contribution

This paper introduces BAGEL, a new quantum chemistry program with unique features like analytical gradients, relativistic wave functions, and innovative electronic structure theories.

Findings

Supports analytical CASPT2 gradients and couplings

Includes relativistic multireference wave functions based on the Dirac equation

Features efficient parallelization using threads and MPI

Abstract

On behalf of the development team, I review the capabilities of the BAGEL program package in this article. BAGEL is a newly-developed full-fledged program package for electronic-structure computation in quantum chemistry, which is released under the GNU General Public License with many contributions from the developers. The unique features include analytical CASPT2 nuclear energy gradients and derivative couplings, relativistic multireference wave functions based on the Dirac equation, and implementations of novel electronic structure theories. All of the programs are efficiently parallelized using both threads and MPI processes. We also discuss the code generator SMITH3, which has been used to implement some of the programs in BAGEL. The developers' contributions are listed at the end of the main text.