Past event
School of Chemistry Colloquium: Professor Stefan Grimme (University of Bonn) Low-cost quantum chemistry methods
Conventional DFT or WFT quantum chemistry schemes are computationally too demanding to globally explore chemical compound, conformer, or reaction space for interesting molecules with about 50-100 atoms. For this purpose a hierarchy of approximate methods mainly based on DFT is discussed.
In the so-called 3c-methods, three corrections for dispersion, BSSE, and BSIE effects are added to small basis set HF or DFT methods. Variants with different amounts of Fock-exchange and AO basis set size were proposed namely HF-3c, PBEh-3c (HSE-3c), and most recently r2SCAN-3c and wB97X-3c. Secondly, the GFN-xTB family of semi-empirical quantum mechanical (SQM) tight-binding methods is discussed. The methods follow a global and element-specific parameters-only strategy and are consistently available for all elements through radon.
Their original purpose has been the computation of molecular Geometries, vibrational Frequencies, and Non-covalent interactions (GFN). The latest GFN2-xTB version includes multipole electrostatic as well as one-center exchange-correlation terms leading to higher accuracy (at lower empiricism) specifically for non-covalent interactions and conformational energies. Furthermore, the extension of the GFN approach to a general purpose force-field is introduced.
Attempts to circumvent the accuracy bottleneck of all SQM methods (minimal AO basis set) are described, which lead to the new PTB approach with a newly developed vDZP basis. The performance of the discussed methods is illustrated for chemically relevant thermochemical
or spectroscopic problems.
School of Chemistry Colloquium. This event is open to final year undergraduate students, MSc students, PhD students, Post-Doctoral Research Fellows and staff.