Structures and physical properties of ∊-FeSi-type and CsCl-type RuSi studied by first-principles pseudopotential calculations

Abstract

An investigation of the relative stability of the two known polymorphs of RuSi, having the 4-FeSi and CsCl structures, has been made by ®rst-principles pseudopotential calculations. The resulting cell volumes and fractional coordinates at P = 0 are in good agreement with experiment. Application of high pressure to the 4-FeSi phase of RuSi is predicted to produce a structure having almost perfect sevenfold coordination. However, it appears that RuSi having the CsCl-type structure will be the thermodynamically most stable phase for pressures greater than 3.6 GPa. Fitting of the calculated internal energy versus volume to a fourth-order logarithmic equation of state led to values (at T = 0 K) for the bulk modulus, K 0 , of 202 and 244 GPa for the 4-FeSi and CsCl phases, respectively, in excellent agreement with experiment. Band-structure calculations for both phases are also presented.

Morphology of the asymmetric iron–silicon interfaces

“…The iron silicide layer at the Si-on-Fe interface shows a thickness of 1.4(1) nm and q ¼ 5:05ð10Þ g/cm 3 . This fitted density is similar to that of the stable stoichiometric -FeSi phase (q ¼ 5:19 g/cm 3 [29]), but it also lies between the value 4.73 g/cm 3 of the highly Fe-defective and epitaxially stabilized c-Fe 0.5 Si [30] and the close to stoichiometric c-Fe 0.88 Si [31], both with the CsCl structure. c-Fe 1Àx Si has been claimed to appear in the Fe/Si interface [18,19,12,15].…”

Resonant X-ray diffraction of α-phase Mo0.15Ru0.85Si and crystal stability calculation in Mo–Ru–Si system (FeSi and CsCl types)

“…Above the 20 bands, an energy gap of about 0.4 eV is observed, which allows classifying the system as a narrow band semiconductor. Our result is in agreement with previous band structure calculations [26][27][28] as well as the electron transport measurements [29,30], revealing both the semiconducting-like character of the temperature-dependent resistivity as well as a large thermopower.…”

High-temperature ab initio calculations on FeSi and NiSi at conditions relevant to small planetary cores

“…It is possible that the stoichiometry of the samples differed sufficiently in the LH-DAC experiments which, when combined with the effect of kinetic inhibition, is enough to explain the large discrepancies between them. Giving credence to this argument is the fact that experiments have shown that small changes in composition affect the structure adopted by RuSi, an analogue material of FeSi; a small excess of Ru (~1%) favours the CsClstructure, whereas samples deficient in Ru show a mixture of ε-FeSi and Ru 2 Si 3 structures (Buschinger et al 1997;Vočadlo et al 2000).…”