Date/Time
Date(s) - 07/05/2024
10:30 am - 11:30 am

Please join us on May 7 for Gabriela Sanchez Diaz’s PhD seminar, which will be offered in-person and online.

Title: Excited state methods for strongly-correlated systems: formulations based on the equation-of-motion approach

Date: Tuesday, May 7, 2023

Time: 10:30 am-11:30 am

Room: ABB A404

Zoom: Please email chemgrad@mcmaster.ca for details.

Host: Paul Ayers

Abstract: The interaction of matter with light, specifically an electromagnetic field, leads to photochemical and photophysical processes. These processes have far-reaching implications for diverse areas of science, environment, and technology. Using theoretical and computational methods helps understand these processes at an atomistic scale. Nonetheless, achieving accurate descriptions of excited states remains an elusive task for current theoretical methods. Tackling this challenge requires developing new approaches that account for electron correlation, going beyond conventional single Slater-determinant-based wavefunction approximations.

The equation-of-motion (EOM) method originated in materials physics and serves as the foundation for many popular approaches for accurately modelling spectra. I will describe this framework and the excited-state wavefunction approximations that can be formulated within it. This ansatz’s versatility lies in its capacity to be combined with dissimilar wavefunction procedures, from single to multireference approaches. Later I will present different EOM formulations, covering aspects such as killer conditions, excitation operator truncation, and reference state wavefunction models. I will illustrate their effectiveness with results on small molecules. Finally, I will discuss our efforts to combine EOM with the Flexible Ansatz for N-electron Configuration Interaction (FANCI), a novel wavefunction approximation framework developed in our group; this extends FANCI’s applicability to spectroscopic properties.