Mid-Term Report Summary - PPOLAH (Predicting Properties of Large Heterogeneous Systems with Optimally-Tuned Range-Separated Hybrid Functionals)
Large-scale heterogeneous systems play a vitally important role in several of the most burning challenges facing materials science. Perhaps most notably, this includes materials systems relevant for basic energy sciences, e.g. for photovoltaics or photocatalysis, but this also includes, e.g. organic/inorganic interfaces crucial for molecular, organic, and hybrid organic/inorganic (opto)electronic systems. Presently, Theory and modelling of such systems face many challenges and would benefit greatly from accurate first principles calculations. However, the “work-horse” of large-scale first principles calculations – density functional theory (DFT) – faces multiple, serious challenges when applied to such systems. This includes the simultaneous treatment of systems with a greatly different chemical nature, correct prediction of energy level alignment, correct prediction of charge transfer states, correct handling of weak interactions, and more. Solving all these problems at the same time within conventional DFT is an extremely difficult functional development problem.
In this project, we pursue a different strategy – we sacrifice the notion that we always seek an all-purpose functional expression and focus instead on per-system physical criteria that can help us fix system-specific parameters without recourse to empiricism. The additional flexibility helps us gain tremendously in simplicity and applicability without any loss of predictive power.
In our work so far, we have:
1. Shown that the approach consistently yields excellent fundamental and optical gaps for molecular systems, including the difficult case of charge transfer excitation.
2. Discovered new fundamental insights into the prediction of gaps from density functional theory.
3. Applied the approach to many important systems.
4. Extended the approach to a full description of the outer-valence electronic structure.
5. Extended the method to the study of molecular crystals.
6. Developed a new approach to the study of doped semiconductor surfaces.
In this project, we pursue a different strategy – we sacrifice the notion that we always seek an all-purpose functional expression and focus instead on per-system physical criteria that can help us fix system-specific parameters without recourse to empiricism. The additional flexibility helps us gain tremendously in simplicity and applicability without any loss of predictive power.
In our work so far, we have:
1. Shown that the approach consistently yields excellent fundamental and optical gaps for molecular systems, including the difficult case of charge transfer excitation.
2. Discovered new fundamental insights into the prediction of gaps from density functional theory.
3. Applied the approach to many important systems.
4. Extended the approach to a full description of the outer-valence electronic structure.
5. Extended the method to the study of molecular crystals.
6. Developed a new approach to the study of doped semiconductor surfaces.