Quantum Nuclear Dynamics in the Condensed Phase
Lead Research Organisation:
University of Cambridge
Department Name: Chemistry
Abstract
The quantum properties of nuclei are determined by the Schroedinger equation, but this equation is much more difficult to solve for nuclei than electrons, with the result that exact quantum dynamics can be obtained from it only for small gas-phase molecules. This project aims to develop approximate methods which will allow quantum dynamics to be simulated in condensed phase systems, such as ice and liquid water. The key idea is that most of the quantum effects in such systems (i.e. zero-point energy and tunnelling) are the result mainly of quantum effects in the Boltzmann statistics; real-time quantum coherences mostly average out. This project will build on a recently developed mixed quantum statistics-classical dynamics method knowns as the 'planetary model', whereby the quantum Boltzmann delocalisation of atomic nuclei is approximated by means of a supplementary 'planet' particle which orbits another particle at the centre of mass of the Boltzmann distribution. This technique allows observable properties such as infrared spectra and neutron-scattering cross sections to be simulated relatively cheaply, and has given very promising results in tests on the infrared spectra of liquid water. This project will focus on extending this methodology to treat non-linear spectra.
Organisations
People |
ORCID iD |
| Stuart Althorpe (Primary Supervisor) | |
| Raz Benson (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509620/1 | 01/10/2016 | 30/09/2022 | |||
| 1942965 | Studentship | EP/N509620/1 | 01/10/2017 | 30/06/2021 | Raz Benson |
| Description | The chemical physics literature contains a wide range of approaches for simulating quantum mechanical effects in condensed-phase systems. This project has focused primarily on methods suitable for calculating infrared spectra from first principles, especially in water, which displays considerable quantum effects even at room temperature. We have generated new understanding of why most of these methods fail to fully capture the complex motion responsible for subtle, yet important, features observed in experimental infrared spectra. We are now making progress in developing a simple, predictive tool to correct for these deficiencies. |
| Exploitation Route | Our findings improve the prospect of highly accurate, first-principles calculations of infrared spectra and related dynamical properties, in aqueous systems and others for which quantum effects are considerable. They are likely to inspire the development of new, efficient simulation tools to that end. Aqueous systems are ubiquitous throughout chemistry and biology, and simulations can play a key role in, for example, understanding the behaviour of biomolecules in different environments. |
| Sectors | Other |