Excited states, symmetry breaking, and multiple solutions in electronic structure theory

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• Dr Hugh Burton, Oxford
• Monday 13 March 2023, 14:30-15:00
• Department of Chemistry, Cambridge, Pfizer Lecture Theatre.

If you have a question about this talk, please contact Dr Christoph Schran.

Zoom link: https://zoom.us/j/92447982065?pwd=RkhaYkM5VTZPZ3pYSHptUXlRSkppQT09

Excited states are essential for understanding photochemical processes, ranging from photosynthesis and biological mechanisms of vision, to photocatalytic reactions and optoelectronics. However, accurate simulations of high-energy, charge transfer, or double excitations remain difficult with state-of-the-art techniques based on linear response theory. This talk will focus on an alternative “state-specific” perspective where excited states are represented by higher-energy variational stationary points of the electronic energy landscape. Firstly, I will describe the structure of the exact electronic energy landscape, the topological properties of exact excited states, and how approximate wave function ansätze form constrained subspaces. I will then characterise the different solutions that can be identified using a single Slater determinant or multiconfigurational wave function approximations in typical molecular systems. These examples highlight that state-specific excitations can provide compact representations of high-energy, charge transfer, and double excitations, while also demonstrating the challenges that must be addressed to achieve practical calculations in the future.

This talk is part of the Lennard-Jones Centre series.

This talk is included in these lists:

• Department of Chemistry, Cambridge, Pfizer Lecture Theatre
• Hanchen DaDaDash
• Lennard-Jones Centre

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