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Abstract:
Magnesium oxide (MgO) is used in a variety of industrial applications due to its low cost and
structural stability. In heterogeneous catalysis, MgO and Li-doped MgO have been studied as catalysts
for the oxidative coupling of methane. In this work, we analyze the structure and stability
of defect complexes comprising Li dopants and oxygen vacancies in MgO, combining scanning tunnelling
microscopy, photon-emission experiments, and density-functional theory computations. The
experimental results strongly indicate that after annealing Li-doped MgO to temperatures of 600 K
and higher, Li evaporates from the surface, but Li defects, such as substitutional defects, interstitials,
or defect complexes comprising Li remain in the bulk. Our calculations show that bulk defect
complexes containing F2+ color centers, that have donated their two electrons to two adjacent Li
defects, are the most stable configurations at realistic pressure and temperature conditions
