Materials Project Seminars – Aron Walsh, "The Ground Truth is Out There"

Title: "The Ground Truth is Out There" Presented as a Materials Project Seminar on February 16th 2022. More information on the Materials Project Seminar Series at https://materialsproject.org/seminars including free registration links for future events and to ask questions about this talk. Speaker: Aron Walsh, Professor, Thomas Young Centre for Theory and Simulation of Materials, Imperial College London, UK Abstract: Density functional theory (DFT) has become a powerful tool for modelling the structures and properties of materials. The first role of a DFT practitioner is to choose an exchange-correlation functional that is appropriate for the chemical system and properties of interest. While there are still issues for describing materials that can be classified as highly correlated, such as those containing partially occupied d or f bands, generally DFT can provide an adequate description for the majority of systems. Indeed, there are a growing number of structure-property databases, including the Materials Project, that conveniently collect large numbers of DFT calculations. Such databases are now being widely used for training statistical machine learning models to reproduce the structure-property correlations of known crystals and also to extrapolate to new chemistries. There is a danger however of forgetting that even if an exact functional was known, the static predictions of DFT calculations for perfect structures do not represent the ground truth. Real crystals are excited and imperfect: the atoms vibrate around their ideal lattice sites; they contain point and extended defects; high energy configurations are accessed by temperature and light. In the context of my own research on semiconducting materials for clean energy applications, I will outline some challenges and possible directions for more accurate materials property predictions.