Handbook of Silicon Based MEMS Materials and Technologies

11.1.2. Silicon Structure Ground State: Elastic Constants and Moduli

The elastic constants provide a description of the elastic response of a solid [25–27]. For single crystals, the second-order elastic constants describe the linear elastic stress–strain response. Higher order elastic constants reflect the nonlinear elasticity of the material [26].

11.1.2.1. Harmonic Approximation and Room Temperatures

The elastic constants are the system energy second derivatives with respect to the strains, defined as(11.5)where u is the elastic displacement. Indeed, when the strains are sufficiently low, one can approximate the elastic energy ΔE stored in ...