Structural and electronic properties of the μ-phase Fe-Mo compounds

Structural (lattice parameters and sub lattice occupancies) and electronic (charge-density and electric field gradient) properties in a series of μ-Fe100−xMox (37.5 ⩽ x ⩽ 44.5) compounds were studied experimentally (X-ray diffraction and Mössbauer spectroscopy) and theoretically (charge and spin self-consistent Korringa-Kohn-Rostoker Green's function method). The lattice parameters a and c showed a linear increase with x while all five lattice sites were found to be populated by both alloying elements: A(1a) and B(6h) predominantly by Fe atoms whereas C(2c) and D(2c′) by Mo atoms hardly depending on the composition. The population of Fe atoms on the site E(2c″) was ranging between ∼50% at x = 37.5 and ∼20% at x = 44.5. Fe-site charge-density (isomer shift) and the electric field gradient (quadrupole splitting, QS) were revealed to be characteristic of the lattice site and both of them were almost x-independent. The difference in the charge-density at Fe-atoms at the sites B (the highest value) and those at the sites D (the lowest value) was estimated as high as 0.18 e. The average charge-density increases linearly with x. The largest QS-values were those at the sites A and C, while the smallest ones at the site D. The average QS-value was 0.25 mm/s.