Thickness effect on the structural, electronic and energetic properties of the cubic KMgF_3 (001) surfaces: A first-principles study

摘要

Using first-principles density functional theory (DFT) calculations, we investigate the (0 0 1) surfaces of fluor-operovskite KMgF3 with KF and MgF2 terminations. The slab layer thickness effects on the structural, electronic and energetic properties are studied. The calculations show that the MgF2 termination presents relatively larger surface rumpling than the KF termination. Both two types of surfaces retain some of the electronic structure characteristics of the bulk, while the band gaps of the surfaces are found to be reduced by about 1.1-1.5 eV with respect to that of the KMgF3 bulk. The surface stability evaluation indicates that the MgF2-terminated surface is energetically more favorable than the KF-terminated surface. Upon increasing the slab thickness from 3 to 11 atomic layers, the surface rumpling, electronic structure and surface energy are found to be slightly affected by the change of slab thickness. Especially, the predicted surface properties are almost the same when the thickness of the slab exceeds 7 atomic layers.