Quantum Theory of Imperfect Crystals

Crystalline materials can be represented, at the atomic scale, by a unit cell that is translated in three dimensions. Point and extended defects break this translational symmetry with profound consequences that can include wave function localisation, variation in the local structure, and the capture or emission of charge carriers and light. The ability to classify, characterise and control defect processes in crystals is critical for many application areas, from energy technologies to quantum computing. First-principles modelling approaches provide access to a range of important defect quantities including energies, vibrations, and electronic excitations for specific species, but challenges remain to enable quantitative comparison with experimental observables. I will discuss recent progress in the theory and simulation of defects in crystals. This talk will cover the importance of defects in solar cell1 and solar fuel2 technologies, as well as our latest work on spontaneous symmetry breaking3. Opportunities and obstacles for the adoption of data-driven approaches for materials informatics will be outlined.

1. “Point defect engineering in thin-film solar cells” J.-S. Park et al, Nat. Rev. Mater. 3, 194 (2018)
2. “Electronic defects in metal oxide photocatalysts” E. Pastor et al, Nat. Rev. Mater. 7, 503 (2022)
3. “Identifying the ground state structures of point defects in solids” I. Mosquera-Lois et al, npj Comp. Mater. 9, 25 (2023)