Lattice Instability during Solid-Solid Structural Transformations under a General Applied Stress Tensor: Example of Si I → Si II with Metallization

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2018-10-19
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Levitas, Valery
Johnson, Duane
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Johnson, Duane
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Mechanical Engineering
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Materials Science and Engineering
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Aerospace EngineeringAmes National LaboratoryMechanical EngineeringMaterials Science and Engineering
Abstract

The density functional theory was employed to study the stress-strain behavior and elastic instabilities during the solid-solid phase transformation (PT) when subjected to a general stress tensor, as exemplified for semiconducting Si I and metallic Si II, where metallization precedes the PT, so stressed Si I can be a metal. The hydrostatic PT occurs at 76 GPa, while under uniaxial loading it is 11 GPa (3.7 GPa mean pressure), 21 times lower. The Si I → Si II PT is described by a critical value of the phase-field’s modified transformation work, and the PT criterion has only two parameters given six independent stress elements. Our findings reveal novel, more practical synthesis routes for new or known high-pressure phases under predictable nonhydrostatic loading, where competition of instabilities can serve for phase selection rather than free energy minima used for equilibrium processing.

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This article is published as Zarkevich, Nikolai A., Hao Chen, Valery I. Levitas, and Duane D. Johnson. "Lattice Instability during Solid-Solid Structural Transformations under a General Applied Stress Tensor: Example of Si I→ Si II with Metallization." Physical Review Letters 121, no. 16 (2018): 165701. DOI: 10.1103/PhysRevLett.121.165701. Posted with permission.

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Mon Jan 01 00:00:00 UTC 2018
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