Surface oxygen vacancy energies

Oxygen vacancy energies, Ed (0), for the surface sites 0(1-3) at the V20s(010) surface with and without surface relaxation. All data are obtained for the V10O31H12-O (= V10O30H12) model cluster [126], In addition, the table contains values of charges and relaxation dis-... 

The dark features ( B in Fig. 5 are less common ( 1 - 2% per surface unit cell) than the oxygen vacancies. They can extend over several unit cells. Upon adsorption of oxygen, the number of the dark spots stays constant within the statistical error. They were tentatively assigned as sub-surface oxygen vacancies [46], however, first-principles total-energy calculations show that such a configuration is highly unlikely [67]. Their nature is unclear at this point. 

Figure 8.8. Oxygen vacancy energy in the Cei.-xZrx02 system as a function of both x and depth (expressed in iattice parameter units) for the (111) and (110) surfaces (from reference 76)...

In LMO (110) surface calculations [851] the 02-terminated slab consisting of seven planes was taken, i.e. four O2 planes and three LaMnO planes. Such a symmetrical slab is nonstoichiometric, i.e. it does not consist of an integer number of formula units. To restore the stoichiometry of the 7-plane slab, one oxygen atom has been removed from both 02-planes terminating the slab, i.e. the slab of three bulk primitive unit cells with periodically repeated surface oxygen vacancies was used. Such an approach is justified since it is weU known that the polar surfaces are stabilized by surface defects and surface-atom relaxation. The smface energy Eg (per surface unit cell) for such a slab equals ... 

The comparison of energies for the stoichiometric and nonstoichiometric 7-plane slabs permits conclusions to be drawn on the role of surface oxygen vacancies in... 

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