Theoretical explanation of the octahedral distortion in FeF2 and MgF2

Autor(en)
Alexander Riss, Peter Blaha, Karlheinz Schwarz, Josef Zemann
Abstrakt

The equilibrium geometries of rutile type FeF2 and MgF 2 are determined using precise density functional theory calculations that lead to good agreement with experimental data. The strong deviation from the "ideal" octahedral geometry in FeF2 comes from the Fe2+ ion with the d6 configuration in the high-spin state, which would require a singly occupied spin-down d orbital. The stability can only be understood by going beyond the first coordination shell considering direct Fe-Fe interactions mainly along the c-axis. The orbital population of the various Fe-d orbitals is analyzed using constraint distortions between the ideal and the equilibrium structure. Above a critical Fe-Fe distance of about 3.15 A° the population numbers change drastically, a single Fe-d spin down orbital becomes occupied and the system can relax to an insulating state. In MgF2 no such d-orbitals are present and thus the distortions are much smaller.

Organisation(en)
Institut für Mineralogie und Kristallographie
Externe Organisation(en)
Technische Universität Wien
Journal
Zeitschrift für Kristallographie : international journal for structural, physical, and chemical aspects of crystalline materials
Band
218
Seiten
585-589
Anzahl der Seiten
5
ISSN
0044-2968
DOI
https://doi.org/10.1524/zkri.218.9.585.20680
Publikationsdatum
2003
Peer-reviewed
Ja
ÖFOS 2012
1051 Geologie, Mineralogie
Link zum Portal
https://ucrisportal.univie.ac.at/de/publications/70e30ffd-f7ca-4370-b963-2aa89c29eb5e