A new high-pressure phase of FeSi

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

“…In contrast to these two studies, Lord et al (2010) find a negative Clausius-Clapeyron slope of −55 MPa/K, also from LH-DAC experiments. This slope is in agreement with multi-anvil press (MAP) experiments carried out by Dobson et al (2002), who found the CsCl-FeSi phase to be stable from 24 GPa and 1950 ± 50 K. Computer simulations show a similar range of transition pressures: ab initio calculations carried out at 0 K in the Generalised Gradient Approximation (GGA) find the transition from ε-FeSi to CsCl-structured FeSi occurring at 13 GPa (Vočadlo et al 1999), 40 GPa (Caracas and Wentzcovitch 2004) and 20 GPa (Zhang and Oganov 2010). Caracas and Wentzcovitch (2004) also carried out calculations using the Local Density Approximation (LDA) and found the transition to occur at 30 GPa.…”

“…Another credible explanation is the possibility of Si diffusion during heating. Dobson et al (2002) used electron microprobe analysis to determine the exact stoichiometry of their samples, but this was not done in the LH-DAC experiments. 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.…”

High-pressure structural behavior of large-void CoSn-type intermetallics: Experiments and first-principles calculations

“…A similar situation has been reported for the FeSi type→ CsCl type high-pressure transformation of FeSi and RuSi. [37][38][39] To evaluate further the stability of CoSn-type FeSn, CoSn, and NiIn, we performed multianvil high-pressure high-temperature experiments.…”

Heavy-impurity resonance, hybridization, and phonon spectral functions inFe1−xMxSi (M=Ir, Delaire1, Al-Qasir2, May3 et al. 2015Phys. Rev. B392190View full textAdd to dashboardCite

“…At low pressure and low temperature, FeSi crystallizes in the B20 cubic structure 13 . It transforms to the simpler B2 phase (CsCl-type) under high pressure and high temperature 14 . The B20 structure can be viewed as a strongly distorted rocksalt structure, with Fe-Si nearestneighbor pairs distorted along 111 directions, resulting in seven-fold coordination at the Fe and Si sites, and low symmetry (T 4 P 2 1 3), 13 .…”

“…Possibly strong electronic correlations have also be noted 34,35 , and it has been proposed that that FeSi could be an unusual d−electron Kondo insulator, although this point remains controversial 32,34,[36][37][38][39] . Interest in FeSi also arises from geophysics, as it is a possible reaction product between molten iron and mantle silicates at the core-mantle boundary 14,[40][41][42] .…”