In the first half of November 2023 two of our PhD students successfully defended their PhD thesis. Underneath you can read a bit more on the work they did at CMM in the past years.
Congratulations Sander and YingXing!
Sander Borgmans
In-Depth Computational Characterization of the Structure and Dynamics in Covalent Organic Frameworks – Monday November 6, 2023
Supervisors: prof. Veronique Van Speybroeck and prof. Sven Rogge
Summary
Throughout history, mankind has demonstrated a remarkable ability to discover, manipulate, and develop materials to address the challenges of their time. Several decades ago, this ingenuity led to the development of nanostructured materials designed with atomic precision. Within this new class of materials, covalent organic frameworks are particularly interesting, endowing an enormous functionality given their internal pore architecture with molecule-sized pores and/or channels. In addition, they are rationally designed through a reticular building block process, allowing them to be tailored toward specific applications. However, this requires a fundamental understanding of their structure, and how this modular structure gives rise to certain properties. The aim of this PhD dissertation is therefore to construct reliable computer models for the structural characterization of covalent organic frameworks and the study of how their structural variations on the nanoscale can have macroscopic consequences. In this way, this research brings theory and experiment closer together, for which various techniques have been developed, or further extended, to enable molecular simulations that can deal with the complexities of these materials at the nanoscale.
YingXing Cheng
Development and Applications of the Frequency-Dependent Polarizable Force Field ACKS2ω – Monday November 13, 2023
Supervisor: prof. Toon Verstraelen
Summary
Van der Waals dispersion interactions are weak yet essential attractive forces critical in chemistry and physics, and their accurate representation remains a challenge in density functional theory (DFT). DFT is widely used for its computational efficiency but often fails to capture the full scope of these interactions, particularly type-C non-additive dispersion, which arise from long-range charge fluctuations, such as those in π-π conjugated systems. This limitation has prompted the development of various correction schemes to improve DFT’s performance, though these typically do not fully account for type-C dispersion.
To remedy the shortcomings in current models, this thesis proposes a novel approach leveraging the adiabatic connection fluctuation-dissipation (ACFD) theorem to capture correlation energies, including type-C dispersion interactions. The complexity of ACFD calculations necessitates a more practical solution, prompting the exploration of a frequency-dependent polarizable force-field method. Specifically, this research focuses on extending the atom-condensed Kohn-Sham DFT approximated to second order (ACKS2), creating a new model, ACKS2ω, which aims to efficiently compute long-range correlation energies using frequency-dependent induced charges and dipoles.