High-temperature and ionization-induced effects in lithium-doped MgO single crystals

The electronic structure of alkali doped alkaline earth metal oxides: Li doping of MgO studied with DFT-GGA and GGA+U

“…When MgO is doped with Li and the temperature is raised to over 1100 K, a new loss feature at 1.60 eV is found, attributed to the formation of the [Li + -O À ] defect. Similar optical transitions have been observed in other studies [1,4].…”

“…Two cluster model studies of Li-doped MgO have been presented, both using unrestricted Hartree-Fock, UHF [12,13]. With an embedded cluster approach Zuo et al [12] found a contraction of 21% in the [Li + -O À ] distance in the defect centre, which is strongly at variance with the experimental findings that the Li-O distance increases [1][2][3][4]. Lintuluoto and Nakamura [13] also used bare cluster models of the (1 0 0) MgO surface, although they found one elongated Li-O distance, at 2.58 Å .…”

“…In EPR and ENDOR studies of Li-doped bulk MgO [1][2][3][4], the presence of hyperfine components in the spectrum was attributed to the formation of a [Li + -O À ] centre with the electronic hole localised on a single oxygen ion. It is also possible to determine the geometry around the defect centre, although the exact [Li + -O À ] distance so obtained depends on the interpretative model used for the data analysis.…”

“…[1][2][3][4], in particular electron spin (paramagnetic) resonance spectroscopy (ESR, EPR) and electron nuclear double resonance spectroscopy (ENDOR) techniques have allowed detailed study of these defect centres, including the elucidation of the nature of charge localisation and the geometry of the [M + -O À ] defect centre.…”

An ab Initio Study on the Oxidative Coupling of Methane over a Lithium-Doped MgO Catalyst: Surface Defects and Mechanism

“…13,[16][17][18][19] In the bulk and on the surface of lithium-doped MgO, Li + ions occupy Mg 2+ sites and stabilize the nearby O -species resulting in [Li + O -] defects. 15,[20][21][22][23][24] Although theoretical studies suggest that [Li + O -] defects can form aggregates, 25 the absence of spin exchange and dipolar broadening in the ESR spectra indicated that the [Li + O -] centers must be well separated from one another by at least 8-10 Å. 20 At elevated reaction temperatures, electron holes can leave bulk Li + impurities, become localized on the surface, and thus increase the number of reactive centers.…”