Validation of Interstitial Iron and Consequences of Nonstoichiometry in Mackinawite (Fe1+xS)
- 22 February 2012
- journal article
- research article
- Published by American Chemical Society (ACS) in The Journal of Physical Chemistry A
- Vol. 116 (9), 2234-2243
- https://doi.org/10.1021/jp206992z
Abstract
A theoretical investigation of the relationship between chemical composition and electronic structure was performed on the nonstoichiometric iron sulfide, mackinawite (Fe1+xS), which is isostructural and isoelectronic with the superconducting Fe1+xSe and Fe1+x(Te1–ySey) phases. Even though Fe1+xS has not been measured for superconductivity, the effects of stoichiometry on transport properties and electronic structure in all of these iron-excess chalcogenide compounds has been largely overlooked. In mackinawite, the amount of Fe that has been reported ranges from a large excess, Fe1.15S, to nearly stoichiometric, Fe1.00(7)S. Here, we analyze, for the first time, the electronic structure of Fe1+xS to justify these nonstoichiometric phases. First principles electronic structure calculations using supercells of Fe1+xS yield a wide range of energetically favorable compositions (0 < x < 0.30). The incorporation of interstitial Fe atoms originates from a delicate balance between the Madelung energy and the occupation of Fe–S and Fe–Fe antibonding orbitals. A theoretical assessment of various magnetic structures for “FeS” and Fe1.06S indicate that striped magnetic ordering along [110] is the lowest energy structure and the interstitial Fe affects the values of moments in the square planes as a function of distance. Moreover, the formation of the magnetic moment is dependent on the unit cell volume, thus relating it to composition. Finally, changes in the composition cause a modification of the Fermi surface and ultimately the loss of a nested vector.Keywords
This publication has 33 references indexed in Scilit:
- Superconductivity in the PbO-type structure α-FeSeProceedings of the National Academy of Sciences of the United States of America, 2008
- Chemically Tuning between Ferromagnetism and Antiferromagnetism by Combining Theory and Synthesis in Iron/Manganese Rhodium BoridesAngewandte Chemie, 2002
- Ferromagnetism in Transition Metals: A Chemical Bonding ApproachAngewandte Chemie, 1999
- From ultrasoft pseudopotentials to the projector augmented-wave methodPhysical Review B, 1999
- Projector augmented-wave methodPhysical Review B, 1994
- Crystal orbital Hamilton populations (COHP): energy-resolved visualization of chemical bonding in solids based on density-functional calculationsThe Journal of Physical Chemistry, 1993
- Explicit, First-Principles Tight-Binding TheoryPhysical Review Letters, 1984
- Über die kristallchemischen parameter der Ni-, Co- und Fe-haltigen phasen vom NiAs-TypJournal of the Less Common Metals, 1976
- Special points for Brillouin-zone integrationsPhysical Review B, 1976
- Linear methods in band theoryPhysical Review B, 1975