High pressure stability of the monosilicides of cobalt and the platinum group elements

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

“…Taking this into account, the stability sequence in FeSi with increasing pressure then becomes MnP-FeSi → ε-FeSi → CsCl-FeSi. This stability sequence is also observed in RuSi, OsSi and CoSi, as predicted by ab initio static calculations similar to those carried out here (Hernandez et al 2015). As with FeSi, Hernandez et al (2015) find the MnP structure in these compounds is only stable at negative pressures at 0 K, with transition pressures of −15, −6.3 and −10 GPa respectively for RuSi, OsSi and CoSi, indicating that (at 0 K) the MnP phase is stabilised as one descends Group 8 from Fe to Os.…”

“…The calculations of Hernandez et al (2015) did not extend past 300 GPa, and so the CsCl-structured phase was not found in either RhSi or IrSi, but it is possible that the same MnP → ε-FeSi → CsCl-FeSi stability sequence would be seen at higher pressures. However, for the silicides of the group 10 elements, Hernandez et al (2015) found a different, possibly more complicated, structural sequence as exemplified by experiments and calculations on NiSi Lord et al 2012;Wood et al 2013;Dobson et al 2016). Lattice dynamics calculations show that the calculated phase boundary between the ε-FeSi and CsCl phases in (2012)].…”

Electron and phonon properties of noncentrosymmetric RhGe from ab initio calculations

“…Actually, the bands computed at other pressures (0, 22, and 43 GPa) look very similar, except the neighborhood of the Г point. The overall shape of the RhGe band structure is much like those previously calculated for other nonmagnetic B20-type TM monosilicides [4][5][6][7] and monogermanides [8,9]. The same is true for the RhGe density of states (DOS) (not depicted) which, in the energy range of interest ( -4 eV to +2 eV), is contributed mostly by the hybridized Rh 4d-and Ge 3p-states, with a dominating contribution from the former.…”

“…One of the three degenerate levels has a zero slope (flat band) and the other two have k-linear dispersions of opposite sign, similar to the Dirac cone in graphene. The same feature situated almost exactly at E F is observed in isoelectronic compounds CoSi, RhSi, and CoGe [5,6,8,9].…”

Effect of Deformation on Topological Properties of Cobalt Monosilicide

“…The stability of CoSi under hydrostatic pressure was theoretically investigated in Ref. [25], where it was predicted that the transition to CsCl structure (Pm3m) take place at hight pressure of 270 GPa. In the present work, we theoreticaly investigate another possibility-the change of band structure under uniaxial strain.…”