Jacob Williams- Defense: LOSC in Translation: Or, The Localized Orbital Scaling Correction for Materials in Periodic Boundary Conditions

Jacob Williams - defense:LOSC in Translation: Or, The Localized Orbital Scaling Correction for Materials in Periodic Boundary Conditions Abstract:Density functional theory (DFT) is a powerful, practical, and widespread method for computing quantum-mechanical properties of molecules and materials. It has been used in thousands of scientific studies, and its foundational papers are among the most cited of all time. However, DFT suffers systematic flaws including delocalization error, which causes (among other inaccuracies) substantially underestimated band gaps. The localized orbital scaling correction (LOSC) is a particularly promising method to correct delocalization error in DFT calculations. LOSC's ability to correct both total energy and orbital energies gives it the potential to correct delocalization error in both molecules and materials with the same theory. Previous work in the Yang group has established its success for molecules. In this work, we extend LOSC to semiconducting and insulating materials. We introduce dually localized Wannier functions, which are localized in space while retaining spectral (energy) information. Correcting delocalization error in materials requires calculating electronic screening, which we compute in three ways: attenuating the Coulomb repulsion, a method we call sLOSC; with accurate, system-dependent linear response (lrLOSC); and with orbital-free linear response (olLOSC). All three methods predict better band gaps than DFT alone; lrLOSC is particularly accurate, with a mean absolute error of 0.29 eV on our test set. Both lrLOSC and olLOSC also correct delocalization error in molecules. Finally, we investigate the possibility that molecular vibrations transmit information about olfactant molecules to smell receptors. We perform computational infrared spectroscopy on the human olfactory receptor OR51E2 bound to propionate (C2H5COO- ). Comparing vibrational energy fluctuations due to the thermal environment to the changes induced by substituting hydrogen isotopes in propionate, we find that only high-frequency vibrational modes are likely to be distinguishable. 10/30/24 1:00pm FFSC 3232