Automatic Generation of Nonpolar Stoichiometric Slab Models Requiring Surface Reconstruction

The slab-and-vacuum model is an indispensable tool to derive energetic, atomistic, and electronic properties of surfaces of materials with first principles codes that employ three-dimensional periodic boundary conditions. Polar and nonpolar slabs require different levels of treatment, as any polar instability must be compensated on a case-by-case basis in the former. Some slabs can be made nonpolar and stoichiometric by simply cleaving from bulk (nonpolar type A and B), while in other cases nonpolar and stoichoimetric slabs can only be attained with surface reconstruction after cleavage (nonpolar type C) [Hinuma et al., Comp. Mater. Sci. 113, 221 (2016)]. In this talk, I will show a procedure exploiting on the crystallographic concept of isometry to automatically reconstruct the topmost and bottommost layers of a nonpolar type C slab to attain stoichiometry. Although this method is not applicable to all nonpolar type C surfaces, automatic generation of nonpolar slabs of many crystals, including perovskite and spinel structures, has now become possible, paving the way toward further understanding of surface physics.