DFT insights into the stoichiometric (001), (011) and (111) thin film surfaces of Ba₂NaIO₆

In this work, first-principles DFT calculations were performed to investigate the geometric, electronic, and magnetic properties of double perovskite Ba₂NaIO₆ (BNIO) in the bulk, and thin film form. The results showed that bulk BNIO in cubic phase (Fm-3m, #225) has a lattice constant of 8.43 Å, and is a non-magnetic direct band gap (E_g) semiconductor with E_g of 2.22 eV. Three types of cleaved surfaces namely (001), (011), and (111) oriented surfaces were considered here. The stability of the surfaces was examined with surface energy (E_s). The E_s is found to be 0.06, 0.09, 0.14 eV/Ų respectively, for (001), (011), and (111) surface, indicating (001) as the energetically most favorable surface. All three surfaces exhibited metallic character, dominated by the splitting of O-p states of the top layer O-atoms. The (001) and (111) surfaces exhibited a magnetic character with magnetic moments of 0.1 and 2.23 μ_B per formula unit, whereas the (011) surface remained non-magnetic.