Density functional theory study of flat and stepped NaCl(001)

The properties of bulk NaCl, NaCl(001), and stepped NaCl(001) surfaces have been examined with density functional theory within the plane-wave pseudopotential approach. Aiming to remedy the lack of quantitative energetic and structural knowledge of such surfaces, we employ the local-density approximation and generalized gradient approximation of Perdew-Burke-Ernzerhof (PBE) exchange-correlation functionals as well as the PBE Wu-Cohen functional [Phys. Rev. B. 73, 235116 (2006)] to determine the surface energy and surface structure of NaCl(001). A range of 9–15 meV/Å2 is obtained for the surface energy of NaCl(001), and the surface is predicted to undergo only small relaxations of the top layer atoms, consistent with low-energy electron diffraction I-V analyses. The isolated step formation energy of monoatomic (100)-like steps on NaCl(001) is estimated to be about 40–60 meV/Å and the interaction energy between adjacent steps is weak. Thermodynamics has been employed to determine the relative stabilities of stoichiometric (100)-like and nonstoichiometric (111)-like steps on NaCl(001), revealing that (100)-like steps are significantly more stable than (111)-like steps at all accessible values of the chlorine chemical potential