Incommensurate structures and radiation damage in Rb₂V₃O₈ and K₂V₃O₈ mixed-valence vanadate fresnoites

The structures and phase transitions to the incommensurate structures in Rb₂V₃O₈ and K₂V₃O₈ mixed-valence vanadate fresnoites are studied with synchrotron single-crystal diffraction as a function of radiation dose at low temperatures and ambient pressure. Strategies to collect and analyse single-crystal diffraction data measured with very intense synchrotron radiation using modern low-noise pixel area detectors are discussed.