ic8b02094_si_001.pdf (259.02 kB)
On Fe–Fe Dumbbells in the Ideal and Real Structures of FeGa3
journal contribution
posted on 2018-10-03, 16:18 authored by Frank R. Wagner, Raul Cardoso-Gil, Benoît Boucher, Maik Wagner-Reetz, Jörg Sichelschmidt, Peter Gille, Michael Baenitz, Yuri GrinThe
intermetallic phase FeGa3 belongs to the rare examples
of substances with transition metals where semiconducting behavior is found. The necessary electron count of 17 ve/fu can be formally derived
from eight Fe–Ga and one Fe–Fe two-center–two-electron
bond. The situation is reminiscent of the well-known Fe2(CO)9 scenario, where a direct Fe–Fe two-center–two-electron
bond was shown to not be present. Fe–Fe interaction in FeGa3 and its substitution variants represents the crucial point
for explanation of electronic, thermal transport, and optical properties
of this material. Chemical bonding analysis in position space of FeGa3 and Fe2(CO)9 on the basis of the topology
of the electron localizability indicator distribution, QTAIM atoms,
two- and three-center delocalization indices, domain natural orbitals,
IQA analysis, and an evaluation of the Fe–Fe dissociation energy
yields a complete picture of the partially compensated Fe–Fe
bond, which is nevertheless strong enough to be of decisive importance.
Structural reinvestigation of differently synthesized single crystals
leads to the composition Fe1+xGa3 (0 ≤ x ≤ 0.018), where the additional
Fe atoms are predicted from DFT/PBE calculations to yield a magnetic
moment of about 2 μB/Fe2 atom and metallic in-gap
states. Accompanying magnetization and ESR measurements are consistent
with this picture.