Theoretical explanation of the octahedral distortion in FeF2 and MgF2
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Alexander Riss
Abstract
The equilibrium geometries of rutile type FeF2 and MgF2 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 constarint distortions between the ideal and the equilibrium structure. Above a critical Fe–Fe distance of about 3.15 Å 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.
© 2003 Oldenbourg Wissenschaftsverlag GmbH
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- The cubic limiting complexes of the tetragonal lattice complexes
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- Plane groups – from basic to advanced crystallographic concepts
- Books Received
Articles in the same Issue
- Theoretical explanation of the octahedral distortion in FeF2 and MgF2
- Rational approximants to 5, 8 and 7-fold two-dimensional tilings
- The cubic limiting complexes of the tetragonal lattice complexes
- The crystal structures of the potassium hydrogen monofluorophosphates, KHPO3F and K3[H(PO3F)2], and the α modification of RbHPO3F
- Electron crystallography of zeolites. 3. Calcined MCM-22 and MCM-49, a case of subtle differences
- Crystal structures, order-disorder transition and twinning of the Jahn-Teller system (NO)2VCl6
- Structural and physical properties of bis(guanidinium) X bis(nitrilotriacetate) hydrate, (C[NH2]3)2X(N[CH2COO]3)2·H2O (X = Zr, Sn, Hf) and bis(methylammonium) X bis(nitrilotriacetate dihydrate, (CH3NH3)2X(N[CH2COO]3)2·2 H2O (X = Sn, Zr)
- Dichloro[(E)-2-chloro-1-vinyl-cyclohexanol](4-methoxy phenyl)Te(IV). A case of conformational polymorphism
- Plane groups – from basic to advanced crystallographic concepts
- Books Received
