Speaker: Lukas Hasecke, Georg-August-Universität Göttingen

The simulation of nuclear quantum effects (NQE) like nuclear delocalization, zero-point vibration, and tunnelling is crucial to accurately describe systems and processes that involve light nuclei especially hydrogen atoms. The significance of these effects has been demonstrated in various fields from biochemistry to condensed matter. [1] In particular, many processes with complex energy landscapes such as proton-coupled electron transfer, hydrogen absorption on surfaces and dynamics at aqueous metal interfaces highlight the tremendous importance of NQEs for an accurate potential energy surface. [2,3]

Although electronic structure theory methods have become standard tools for quantum chemical investigations, addressing NQEs still lacks computationally accessible and straightforward approaches. To tackle this challenge, we combined the elegant and computationally efficient Nuclear-Electronic Orbital framework developed by Hammes-Schiffer and coworkers with local and canonical density fitting approximations. [4,5] This combination provides new low-order scaling methods, which for the first time allow to include NQEs of large systems within a few hours and for small to medium-sized systems in minutes.

We demonstrate the accuracy and transferability of our approach by benchmarking it to real use cases relevant to chemical, biological, and material science applications. Thereby, emphasizing the necessity of employing multicomponent energy surfaces to match with experimental conclusions. [5,6] Overall, our methods provide a compelling instrument to include NQEs within PESs with exceptional computational efficiency and marks a significant step towards an accurate ab-initio simulation with wide-ranging applications from material design to energy conversion.

1. T. Markland, M. Ceriotti Nat Rev Chem 2 0109 2018
2. A. J. Coffman, et al. JCP 152 (23) 2020
3. L. Yan, et al. Phys. Rev. B 101165414 2020
4. L. Hasecke, R. A. Mata JCTC 19 8223-8233 2023
5. L. Hasecke, et al. JPCA 129 15 3560-3566 2025
6. L. Hasecke, R. A. Mata JCTC 20 9928-9938 2024