Exploring the accuracy limits of lattice strain quantification with synthetic diffraction data

From a collection of scattering vectors obtained by synchrotron X-ray diffraction, the lattice strain can be spatially quantified. This paper explores the inherent accuracy limits by comparing a least-squares regression and an optimization method applied to synthetic diffraction data excluding any measurement uncertainties potentially present in real experiments. The optimization method in combination with a novel fitness function can identify the deviatoric/full lattice deformation gradient with accuracy better than 10⁻⁹. The least-squares regression is much less accurate unless all scattering vector lengths are known, in which case the exact lattice deformation gradient can be recovered.