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

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Date

2022-02-21

Authors

Levitas, Valery
Levitas, Valery I.
Popov, Dmitry
Velisavljevic, Nenad

Publisher

Springer Nature

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Authors

Levitas, Valery

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Organizational Units

Aerospace Engineering

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Mechanical Engineering

Organizational Unit

Ames Laboratory

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Department

Aerospace EngineeringMechanical EngineeringAmes Laboratory

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 {111} interface with Si-I and produce almost self-accommodated nanostructure despite the large transformation volumetric strain of −0.237. The interfacial bands arrest the {111} interfaces, leading to repeating nucleation-growth-arrest process and to growth by propagating {110} interface, which (as well as {111} interface) do not appear in traditional crystallographic theory.

Comments

This article is published as Chen, Hao, Valery I. Levitas, Dmitry Popov, and Nenad Velisavljevic. "Nontrivial nanostructure, stress relaxation mechanisms, and crystallography for pressure-induced Si-I→ Si-II phase transformation." Nature Communications 13, no. 1 (2022): 1-6. DOI: 10.1038/s41467-022-28604-1. Copyright 2022 The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License. Posted with permission.