We have a new paper release ! On May 3rd, 2022, TIMEleSS student Matthias Krug, PI Carmen Sanchez-Valle, and PI Sébastien Merkel published a paper in Physical Review Materials, along with Binbin Yue and Fang Hong from the Center for High Pressure Science & Technology in Beijing, China.
The paper focuses on deformation in MnO2 and particularly its high pressure phase, in the CaCl2 structure. Why do we care about MnO2 ? MnO2 is not a deep Earth material, but it can be used as an analogue for SiO2 stishovite, which crystalizes in a rutile structure at low pressure and transform to a denser CaCl2 structure under high pressure. In SiO2, the stishovite to post-stishovite transformations occurs at ~ 50 GPa and is not always easily reached in deformation experiments. In MnO2, this same structural transition occurs at much lower pressure, around 4 GPa.
Our results show that, after phase transition to a CaCl2 structure above 3.5 GPa, the dominant (010)[100] and secondary {110}[001] and {011}[0-11] slip systems induce a 121 texture in compression. Further compression increases the activity of the {011}⟨0−11⟩ slip system, with an enhanced 001 texture at ∼50GPa. Finally, MnO2 transforms back to a rutile structure upon pressure release, with a significant orientation memory, highlighting the martensitic nature of the CaCl2 to rutile structural transformation. Overall, these results help us understanding plasticity and microstructures of CaCl2-structured dioxides, with implications in materials and Earth and planetary science.
The full reference for the study: B Yue, M. Krug, C. Sanchez-Valle, S. Merkel, and F. Hong, Deformation and slip systems of CaCl2-type MnO2 under high pressure, Phys. Rev. Mater., 6, 053603 (2022) [doi: 10.1103/PhysRevMaterials.6.053603]