A note on the relation of anisotropic peak broadening with lattice symmetry in powder diffraction

A bridge is established between the Gregorkiewitz & Boschetti [Acta Cryst. (2024), A80, 439-445] and Stephens [J. Appl. Cryst. (1999), 32, 281-289] formalisms of anisotropic peak broadening in powder diffraction. The paper by Gregorkiewitz & Boschetti presented formulas describing position shifts of low-symmetry peaks due to different lattice relaxation schemes. Anisotropic peak broadening caused by lattice relaxation can be parameterized by the variance of slightly dispersed peaks' positions. The calculated variances are compared with formulas from the widely used phenomenological model of anisotropic peak broadening by Stephens. Specific relations between anisotropic peak broadening parameters can be a hint of a possible unresolved peak splitting due to lattice symmetry lowering.