1, 0.1) eV. The yellow-curved isosurfaces stand for the charge density of 0.6 a.u.-3. Since VOs are more likely to form at the subsurface (LaO layer) than the surface in the Pd-containing FeO2-terminated surface, we placed another VO in the same LaO layer (Figure  2 group III (a) to (c)). If two VOs are both located at the subsurface, the second Pd atom tends to substitute the Fe atom either at the second FeO2 layer forming a pair of Pd atoms (Figure  2 group III (b)) or on the surface

forming the PdO2 layer (Figure  2 group III (c)). The difference in energy between these two configurations is less than 0.05 eV. Thus, the additional VO stabilizes the PdO2-layer exposed to the vacuum. Thus Selleckchem PR 171 far, we have assumed the existence of VO. However, the concentration of VOs depends on their formation energy. Therefore, we have to verify the stability of surfaces containing VO(s) with different concentrations of Pd by taking the formation energy of VOs into account to further strengthen our conclusion. We calculated the relative energies of surfaces containing Pd m VOn (m =1 and 2 and n =0, 1, and 2) relative to the perfect slab (without VOs) with Pd inside the bulk of LFO (see Figure  2 group

I (a)). Note that the systems we have discussed here are surfaces with Pd atom(s) and VO(s) located on/near the surface. The relative energies (ΔE rel) as a function of the chemical potential of oxygen (Δμ O ) are shown in Figure  4. The corresponding SB431542 purchase geometries for the Pd m VOn -containing surfaces are all included in Figure  2. Since two Pd atoms fail to segregate near/at the surface adjacently without VOs, the results for the Pd2-containing Cediranib (AZD2171) perfect surface excluded from Figure  4. The ΔE rel for each colored line is calculated as: (1) (2) (3) (4) (5) where the first items in Equations 1 to 5 on the right-hand side are the total energies of the Pd m VOn -containing

(m =1 and 2 and n =0, 1, and 2) surfaces, with their subscripts describing their compositions. represents the total energy of the reference surface that contains one solid-solution state of Pd inside the bulk. The in Equations 4 and 5 is the total energy of the pristine FeO2-terminated surface. The μ O is the chemical potential of oxygen. The chemical potentials of oxygen in the LFO bulk and gas phase are equal under equilibrium conditions. The μ O based on an ideal gas approximation is directly connected with the partial pressure (p (O2)) and temperature (T) by (6) (7) in which k is the Boltzmann constant and p 0 is taken to be the standard pressure. is the total energy of an isolated O2 molecule. The item is determined by using thermodynamic data from the thermochemical tables [26]. Hence, we can obtain the formation energy of VO(s) based on Equations 2 to 5 by subtracting the item in Equation 1.