NSF/DMR-BSF: Density Functionals for Predictive Excited-State Calculations of Solids

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NONTECHNICAL SUMMARYThe National Science Foundation and the United States -- Israel Binational Science Foundation (BSF) jointly support this collaboration between a US-based researcher and an Israel-based researcher. The NSF Division of Materials Research funds this award, which supports research and education on the development of advanced computational methods for the simulation and prediction of materials properties.The discovery and development of new materials for converting sunlight into electricity is significantly limited by not having detailed understanding of how materials harvest light, transduce energy, and transport electric charge. All these phenomena are a challenge to model computationally as they involve excited electronic states. There exist computational methods with predictive power for such processes, but they come at significant computational cost. Developing more computationally efficient alternative approaches that offer similar accuracy would enable predictions for increasingly complex materials and would facilitate adapting such methods for materials discovery and design. This research project lays important groundwork toward the development of such efficient predictive approaches for real materials. Central to the proposed effort is outreach to and mentoring of next-generation computational materials theorists at all age levels, augmented by targeted recruitment of women and other underrepresented-minority undergraduate and graduate students. The PI will also organize tours of local research facilities for undergraduate, elementary, and middle-school students - as well as educators - in the Bay area and beyond. The US-based graduate students will travel to Israel to carry out research at the Israeli PI's group.TECHNICAL SUMMARYThe National Science Foundation and the United States -- Israel Binational Science Foundation (BSF) jointly support this collaboration between a US-based researcher and an Israel-based researcher. The NSF Division of Materials Research funds this award, which supports research and education on the development of advanced computational methods for the simulation and prediction of materials properties.In materials and condensed matter physics, the formalism of choice for quantitative determination of the band structure has long been many-body perturbation theory. This formalism has yielded excellent electronic structure predictions for many different classes of metals, semiconductors, and insulators. However, these predictions come at significant computational cost; extracting band structures from density functional theory (DFT), based on the single-electron energies and orbitals obtained from the solution of the Kohn-Sham equation, could alleviate this cost. The project involves a binational theoretical and computational collaboration to develop a new class of density functionals - optimally tuned range-separated hybrid (OTRSH) functionals - capable of predicting accurate quasiparticle band gaps and band structures, and optical spectra, including electron-hole interactions, for a range of complex solid-state materials, with greater computational efficiency than existing approaches. Using a benchmark set of well-studied materials, the team will: i) determine range-separation parameters that lead to the best match between OTRSH and the leading-edge excited-state method for each of these compounds; ii) develop the physics of the range-separation parameters; and iii) advance the OTRSH approach. The research team will then apply the OTRSH approach to a range of complex systems of contemporary interest, including transition metal oxides, Dirac materials, halide perovskites, and two-dimensional materials. The research activity will also address several open questions systematically, and ultimately develop an efficient DFT approach for understanding existing and predicting new excited-state phenomena in complex materials.Central to the proposed effort is outreach to and mentoring of next-generation computational materials theorists at all age levels, augmented by targeted recruitment of women and other underrepresented-minority undergraduate and graduate students. The PI will also organize tours of local research facilities for undergraduate, elementary, and middle-school students - as well as educators - in the Bay area and beyond. The US-based graduate students will travel to Israel to carry out research at the Israeli PI's group.