A Reusable Library for Second-Order Orbital Optimization Using the Trust Region Method
Abstract
We present a reusable, open-source software implementation of the second-order trust region algorithm in the new OpenTrustRegion library. We apply the implementation to the general-purpose optimization of molecular orbitals in various contexts within electronic-structure theory. Our permissibly licensed implementation can be included in any software package, be it free and open-source, academically licensed closed-source, or commercial. Detailing the implementation in OpenTrustRegion, we present a review of the theory behind trust region-based methods alongside various extensions. We demonstrate the robustness and efficiency of our optimization library with extensive benchmarks for self-consistent field calculations, orbital localization, as well as orbital symmetrization tasks, featuring challenging and pathological systems.
Cite
@article{arxiv.2509.13931,
title = {A Reusable Library for Second-Order Orbital Optimization Using the Trust Region Method},
author = {Jonas Greiner and Ida-Marie Høyvik and Susi Lehtola and Janus J. Eriksen},
journal= {arXiv preprint arXiv:2509.13931},
year = {2025}
}
Comments
31+20 pages, 5 figures. SI and selected geometries as ancillary files