Details

Autor(en) / Beteiligte

• Widatallah, H.M.
• Moore, E.A.
• Babo, A.A.
• Al-Barwani, M.S.
• Elzain, M.

Titel

Atomistic simulation and ab initio study of the defect structure of spinel-related Li{sub 0.5−0.5x}Mg{sub x}Fe{sub 2.5−0.5x}O{sub 4}

Ist Teil von

• Materials research bulletin, 2012-12, Vol.47 (12)

Ort / Verlag

United States

Erscheinungsjahr

2012

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Graphical abstract: Unit cell of Li0{sub 5−0.5x}Mg{sub x}Fe{sub 2.5−0.5x}O{sub 4}, showing the lowest energy structure obtained using interatomic potential and DFT ab initio calculations. Large white spheres O{sup 2−}; small light grey spheres Mg{sup 2+} (evenly substituting of Li{sup +} and Fe{sup 3+} at octahedral sites); small dark grey spheres Fe{sup 3+}; small black spheres Li{sup +}. Display Omitted Highlights: ► Defect structure of Li{sub 0.5−0.5x}Mg{sub x}Fe{sub 2.5−x}O{sub 4} is studied with atomistic and DFT methods. ► 19 possible defect structure models with ∼60 defect configurations are investigated. ► The most favourable model found is when Mg{sup 2+} ions evenly replace Li{sup +} and octahedral Fe{sup 3+}. ► This defect structure decreases the magnetisation relative to that of Li{sub 0.5}Fe{sub 2.5}O{sub 4}. ► Experimentally-deduced models, at variance with the one obtained here, are discussed. -- Abstract: The position of magnesium ions in Mg{sup 2+}-doped lithium ferrite of the composition Li{sub 0.5−0.5x}Mg{sub x}Fe{sub 2.5−0.5x}O{sub 4}, which has been a matter of uncertainty among some experimentalists, is investigated using interatomic potential and ab initio DFT calculations. Among possible 19 defect structure models, some of which have been reported experimentally to be the most favorable, the lowest energy is found for Mg{sup 2+} ions evenly replacing Li{sup +} and Fe{sup 3+} ion on octahedral sites. This gives a decrease in magnetisation for the Mg{sup 2+}-doped ferrite relative to the un-doped lithium ferrite. The results suggest that some experimental observations of increased magnetisation of spinel lithium ferrite on Mg{sup 2+}-doping could be due to substitution of Mg{sup 2+} or Li{sup +} on tetrahedral sites at the high temperatures used in preparation of the solid and/or the presence of undetected defects in the initial precursors.