Band Energy Dependence of Defect Formation in Cd₃As₂

Cadmium Arsenide (Cd­₃As₂) is a prototypical Dirac semimetal, manifesting topological properties in a 3D bulk material. In defect-free Cd₃As₂, the Fermi level E_F lies at a minimum in the density of states at the Dirac point, but Cd₃As₂ forms as intrinsically n-type with an elevated E_F. Therefore, Fermi level control is desirable to fully access and utilize the topological features. To elucidate the interplay between electronic structure and doping, we performed band structure and defect calculations using the SCAN meta-GGA functional with inclusion of spin-orbit coupling and the 80-atom primitive cell of the Cd₃As₂ ground state (space group # 142).

The SCAN functional maintains the band structure topology of DFT functionals but induces significant quantitative changes in the band energies near the Dirac point, raising the energies of bands with s-like character relative to E_F. At the same time, the formation energies for electron donating and accepting defects in Cd₃As₂ have an innate concentration dependence based upon the occupation and depopulation of band states above and below the Dirac point, respectively. We show that the band energies of defect free Cd₃As₂ can be used to extrapolate the defect formation energies to specific electron concentrations.