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Effect of the fcc-hcp martensitic transition on the equation of state of solid krypton up to 140 GPa

By A. ROSA, G. Garbarino, R. Briggs, V. Svitlyk, Guillaume Morard, Mohamed Ali Bouhifd, J. Jacobs, T. Irifune, O. Mathon and S. Pascarelli


International audienceSolid krypton (Kr) undergoes a pressure-induced martensitic phase transition from a face-centered cubic (fcc)to a hexagonal close-packed (hcp) structure. These two phases coexist in a very wide pressure domain inducingimportant modifications of the bulk properties of the resulting mixed phase system. Here, we report a detailedin situ x-ray diffraction and absorption study of the influence of the fcc-hcp phase transition on the compressionbehavior of solid krypton in an extended pressure domain up to 140 GPa. The onset of the hcp-fcc transformationwas observed in this study at around 2.7 GPa and the coexistence of these two phases up to 140 GPa, themaximuminvestigated pressure. The appearance of the hcp phase is also evidenced by the pressure-induced broadening andsplitting of the first peak in the XANES spectra. We demonstrate that the transition is driven by a continuousnucleation and intergrowth of nanometric hcp stacking faults that evolve in the fcc phase. These hcp stackingfaults are unaffected by high-temperature annealing, suggesting that plastic deformation is not at their origin.The apparent small Gibbs free-energy differences between the two structures that decrease upon compressionmay explain the nucleation of hcp stacking faults and the large coexistence domain of fcc and hcp krypton. Weobserve a clear anomaly in the equation of state of the fcc solid at ∼20 GPa when the proportion of the hcp formreaches ∼20%.We demonstrate that this anomaly is related to the difference in stiffness between the fcc and hcpphases and propose two distinct equation of states for the low and high-pressure regimes

Topics: [SDU.STU.PE]Sciences of the Universe [physics]/Earth Sciences/Petrography
Publisher: 'American Physical Society (APS)'
Year: 2018
DOI identifier: 10.1103/PhysRevB.97.094115
OAI identifier: oai:HAL:hal-01773713v1
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