py-sc-fermi: self-consistent Fermi energies and defect concentrations from electronic structure calculations

Abstract

py-sc-fermi is a Python package for calculating point-defect concentrations in crystalline materials, under the constraint of net–charge-neutrality and the assumption of thermodynamic (quasi-)equilibrium. The required inputs are the formation energies of all point defects of interest and the electronic density of states. These can be obtained from electronic structure calculations, e.g., density functional theory. Point defects are atomic-scale imperfections in crystalline materials. They can strongly affect a range of material properties, including electronic structure (Pastor et al., 2022), charge transport (Maier, 2015), and energy-conversion processes (Kim et al., 2020). Point defect concentrations are generally sensitive to synthesis conditions and to the inclusion of extrinsic dopants. By understanding the thermodynamics of point-defect formation, it is possible to predict the response of specific material properties to changes in synthesis or doping protocols (Park et al., 2018; Qu et al., 2022; Squires et al., 2019). The quantitative modelling of point-defect populations in functional materials has become common practice in the materials modelling community, often undertaken with the aim of informing the design of novel, highly performant materials (Ganose et al., 2018; Jackson et al., 2022; Toriyama et al., 2021) or to rationalise and optimise the properties of known materials (Kim et al., 2018; Shimoda et al., 2022; Squires et al., 2022).