Quantum tunnel effect: dynamics of molecules with quantum nuclei

Project funded by Croatian Science Foundation (HRZZ) (Research Projects), grant IP-2020-02-9932. Participating organisations named by the source: Prirodoslovno-matematički fakultet, Zagreb; University of Zagreb, Faculty of Science. Funded amount: EUR 104,059, as stated by the source. Runs 2021-01-18 to 2025-06-17. Keywords: instantons, tunnelling splitting, path-integral methods, quantum molecular dynamics, tunnelling rate. Source: OpenAIRE Graph, from the funder's project data (collected by OpenAIRE on 2026-07-23); national funding data, not CORDIS. Abstract given by the source: Quantum tunnelling plays an important role in dynamics and spectroscopy of molecules. It can significantly affect reactivity and allow molecular rearrangements which would otherwise be forbidden. Instanton method provides a way to approximate and visualise tunnelling dynamics using an optimal tunnelling path along which the quantum process predominantly take place. It relies on the optimization of the path, thus it enables us to treat much larger molecular systems in full dimensionality or rely on more accurate on-the-fly electronic potentials than the more accurate methods. The aim of this project is to extend the domain of applicability of the instanton method and to increase its efficiency in order to study systems that would otherwise be inaccessible. Specifically, we aim to develop a new instanton theory to calculate tunnelling splittings in vibrationally excited states and rotational energies. We will apply those theories to study tunnelling spectra in water clusters that have recently been measured, which will provide tests of water potentials at far-from-equilibrium geometries and insights into dynamics of hydrogen bonds, how they break, form and rearrange. Further applications envisage the study of the substituent effect on hydrogen bonds in some substituted carboxylic acid dimers through the associated tunnelling splittings. We also aim to develop methods for efficiently locating optimal tunnelling paths for rate calculations in nonadiabatic systems. These will be applied to study photo-excited nonadiabatic dynamics of indole or phenol and interpret time-resolved photoelectron spectra using a combination of surface-hopping dynamics above the H atom detachment barrier and instantons for the dissociation rates below the barrier. Finally, we will apply our methods to calculate tunnelling rates for selected free radical reactions which take place in aqueous solutions to determine mechanisms and estimate kinetic isotope effect.

Original source.

Source: OpenAIRE Graph: projects of national funders, OpenAIRE, from the project data of Croatian Science Foundation (HRZZ). Retrieved 2026-10-28. Licence: Creative Commons Attribution 4.0 (OpenAIRE Graph). Selected metadata, adapted presentation; the publisher's record is authoritative. No endorsement by the source is implied. Licence: Creative Commons Attribution 4.0 (CC BY 4.0).

AI-assisted summary: The project "Quantum tunnel effect: dynamics of molecules with quantum nuclei" is funded by the Croatian Science Foundation with a grant of EUR 104,059, running from January 18, 2021, to June 17, 2025. It involves the University of Zagreb and focuses on quantum tunnelling in molecular dynamics. Suggested technology pillar: simulation. Generated by AI from the public source text; it may contain errors and the original source is authoritative.