Henry Snowden
PhD student, September 2023-present
PhD Project
My reasearch aims to explain how laser-generated excited electrons evolve over time and then how they can interact with adsorbates on a metal surface. The motivation behind this is to be able to probe photocatalytic reactions on surfaces and determine what reaction mechanisms are taking place in order to udnerstand the properties taht make good photocatalysts for different reactions. There has been lots of experimental work performed in this area but distinguising concretely between charge transfer mechanisms (direct or indirect), phonon coupling or photothermal heating is difficult and time consuming therefore we want to be able to do this computaitonally by switching on and off different mechansisms.
My current priority is finding an accurate and computationally efficient way to model how the electron distribution in a metal changes over time after exposure to a defined laser pulse. The current main approaches to this problem is via either the Two-Temperature Model (TTM) or the Boltzmann Transport Equation (BTE). The downside to the former is that it completely ignores the presence of non-equilibrium electrons, which experimentally have been shown to be important in may reactions, while the altter captures all effects but is a very expensive process limiting the flexibility of the method.
I have decided to improve an intermediary method called the Extended Two-Temperature Model (ETTM) which can capture the non-equilibrium electrons but still in a simplistic way reminiscient of the TTM. I hope to be able to then utilise these distributions within non-adiabatic surface dynamics methods such as surface-hopping in order to determine the effect of non-equilibrium electrons on photocatalytic processes at surfaces.
Background
I did my M.Chem at the University of Liverpool in computational chemistry where I did a B.Sc reserach project, with Dr. Dyer, using DFT to determine activation energies in CO2 reduction on intermetallic materials. I then did my M.Chem project, with Dr. Darling, where I used DFT and STM simulations to determine the structure of ice formations on highly stepped surfaces.