The phase diagram of NiSi under the conditions of small planetary interiors

Dobson, David; Ahmed, Jabraan; Walker, Andrew M.; Lathe, Christian; Whitaker, Matthew; Vočadlo, Lidunka; Wood, Ian G.; Santangeli, James; Wann, Elizabeth T. H.; Hunt, Simon A.; Morard, Guillaume; Lord, Oliver T.; Mueller, Hans J.; Baron, Marzena A.; Mezouar, Mohamed; Thomson, Andrew R.

doi:10.1016/j.pepi.2016.10.005

Journal Article

PUBDB-2016-05327

The phase diagram of NiSi under the conditions of small planetary interiors

Dobson, D. (Corresponding author)Extern* ; Hunt, S. A. ; Ahmed, J. ; Lord, O. T. ; Wann, E. T. H. ; Santangeli, J. ; Wood, I. G. ; Vočadlo, L. ; Walker, A. M. ; Thomson, A. R. ; Baron, M. A.Extern* ; Mueller, H. J.Extern* ; Lathe, C.Extern* ; Whitaker, M. ; Morard, G.Extern* ; Mezouar, M.Extern*

2016
Elsevier Science Amsterdam [u.a.]

Physics of the earth and planetary interiors 261, 196 - 206 (2016) [10.1016/j.pepi.2016.10.005]

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Please use a persistent id in citations: doi:10.1016/j.pepi.2016.10.005 doi:10.3204/PUBDB-2016-05327

Abstract: The phase diagram of NiSi has been determined using in situ synchrotron X-ray powder diffraction multi-anvil experiments to 19 GPa, with further preliminary results in the laser-heated diamond cell reported to 60 GPa. The low-pressure MnP-structured phase transforms to two different high-pressure phases depending on the temperature: the ε-FeSi structure is stable at temperatures above ∼1100 K and a previously reported distorted-CuTi structure (with Pmmn symmetry) is stable at lower temperature. The invariant point is located at 12.8 ± 0.2 GPa and 1100 ± 20 K. At higher pressures, ε-FeSi-structured NiSi transforms to the CsCl structure with CsCl-NiSi as the liquidus phase above 30 GPa. The Clapeyron slope of this transition is −67 MPa/K. The phase boundary between the ε-FeSi and Pmmn structured phases is nearly pressure independent implying there will be a second sub-solidus invariant point between CsCl, ε-FeSi and Pmmn structures at higher pressure than attained in this study. In addition to these stable phases, the MnP structure was observed to spontaneously transform at room temperature to a new orthorhombic structure (also with Pnma symmetry) which had been detailed in previous ab initio simulations. This new phase of NiSi is shown here to be metastable.

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