easyunfold: A Python package for unfolding electronicband structures

The electronic band structure is an important property for understanding and designing solid crystalline materials in many fields such as photovoltaic, catalytic, thermoelectric and transparent-conducting materials. Obtaining the band structure for an ideal crystal through firstprinciples density functional theory (DFT) calculations is a well-established routine operation (Ganose et al., 2018). However, the materials of interest are often complex and the simulation cells may contain multiple primitive cells of the archetypal structure when, for example, modelling disordered or defective materials (Kim et al., 2020). Repeating the unit cell in real space results in folded band structures, as illustrated in Figure 1, complicating its interpretation and analysis. Band structure unfolding maps the electronic structure from supercell calculations back to the reciprocal lattice of the primitive cell, thereby enabling researchers to understand structure-property relationships and compare the effect of various crystal imperfections on an equal footing. With easyunfold, we provide a simple, easy-to-use, yet powerful and flexible tool which implements the band structure unfolding workflow using plane-wave DFT codes, from input file generation to publication-quality plotting.