Determination of internal strain by optical measurements

Strain-induced atomic displacements can be determined by diffraction experiments only in the case of extraordinarily favorable conditions. I propose optical measurements as an alternative method for determining components of internal strain. Based on the bond-charge model, optical and structural quantities are related by bond parameters. They are obtained from the optical constants of selected materials. Then, internal displacements are determined by piezo-optical measurements. The method is demonstrated with the bonds Ge-O and Si-O and its reliability is tested. Its sensitivity is six orders of magnitude higher than the sensitivity obtained in diffraction experiments.