Equation of State, Stability, Anisotropy and Nonlinear Elasticity of Diamond-Cubic (ZB) Silicon by Phonon Imaging at High Pressure

TL;DR

This study uses phonon imaging under high pressure to accurately determine the elastic properties, stability, and anisotropy of single-crystalline silicon in the diamond cubic phase, revealing the importance of nonlinear elasticity effects.

Contribution

It demonstrates the effectiveness of phonon imaging in measuring elastic constants of silicon up to phase transition and revises the understanding of nonlinear elasticity in cubic silicon.

Findings

Elastic constants measured up to 10 GPa

Nonlinear elasticity terms are significant beyond third-order

Silicon's mechanical stability and anisotropy are pressure-dependent

Abstract

Experimental phonon imaging in diamond anvils cell is demonstrated to be an adequate tool to extract the complete set of elastic constants of single-crystalline silicon up to the ZB$\rightarrow \beta-$Sn transition (10 GPa). Contrary to what was commonly admitted, we demonstrate that the development of the strain-energy density in terms of strains cannot be stopped, for silicon, after the terms containing the third-order elastic constants. Nonlinear elasticity, degree of anisotropy and pressure-induced mechanical stability of the cubic silicon structure are thus revisited and investigated in more detail.