5. Anharmonicity and Raman shift under stress: imaging stresses

One of the special features of the Raman imaging technique is its dual physico-chemical and mechanical analysis. Indeed, as the name suggests, the dynamics of atoms determine mechanical properties. The macroscopic mechanical properties of a heterogeneous material are a function of the residual stress state of its constituents, fixed at the time of elaboration (by the expansion differential between phases) or modified subsequently. A stress Δσ applied on a macroscopic scale will be reflected on a molecular or atomic scale by a deformation Δe (%) of the chemical bonds and vice versa