Nontrivial nanostructure, stress relaxation mechanisms, and crystallography for pressure-induced Si-I → Si-II phase transformation

Hao Chen; Valery I Levitas; Dmitry Popov; Nenad Velisavljevic

doi:10.1038/s41467-022-28604-1

Nontrivial nanostructure, stress relaxation mechanisms, and crystallography for pressure-induced Si-I → Si-II phase transformation

Nat Commun. 2022 Feb 21;13(1):982. doi: 10.1038/s41467-022-28604-1.

Authors

Hao Chen¹, Valery I Levitas^{2

3}, Dmitry Popov⁴, Nenad Velisavljevic^{5

6}

Affiliations

¹ Key Laboratory of Pressure Systems and Safety, Ministry of Education, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai, 200237, People's Republic of China.
² Iowa State University, Departments of Aerospace Engineering and Mechanical Engineering, Ames, IA, 50011, USA. vlevitas@iastate.edu.
³ Ames Laboratory, Division of Materials Science and Engineering, Ames, IA, USA. vlevitas@iastate.edu.
⁴ HPCAT, X-ray Science Division, Argonne National Laboratory, Lemont, IL, USA. dpopov@anl.gov.
⁵ HPCAT, X-ray Science Division, Argonne National Laboratory, Lemont, IL, USA.
⁶ Physics Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA.

Abstract

Crystallographic theory based on energy minimization suggests austenite-twinned martensite interfaces with specific orientation, which are confirmed experimentally for various materials. Pressure-induced phase transformation (PT) from semiconducting Si-I to metallic Si-II, due to very large and anisotropic transformation strain, may challenge this theory. Here, unexpected nanostructure evolution during Si-I → Si-II PT is revealed by combining molecular dynamics (MD), crystallographic theory, generalized for strained crystals, and in situ real-time Laue X-ray diffraction (XRD). Twinned Si-II, consisting of two martensitic variants, and unexpected nanobands, consisting of alternating strongly deformed and rotated residual Si-I and third variant of Si-II, form [Formula: see text] interface with Si-I and produce almost self-accommodated nanostructure despite the large transformation volumetric strain of [Formula: see text]. The interfacial bands arrest the [Formula: see text] interfaces, leading to repeating nucleation-growth-arrest process and to growth by propagating [Formula: see text] interface, which (as well as [Formula: see text] interface) do not appear in traditional crystallographic theory.

Abstract

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