title: Pushing the limits of crystallography.
abstract: A very serious concern of scientists dealing with crystal structure refinement, including theoretical research, pertains to the characteristic bias in calculatedversusmeasured diffraction intensities, observed particularly in the weak reflection regime. This bias is here attributed to corrective factors for phonons and, even more distinctly, phasons, and credible proof supporting this assumption is given. The lack of a consistent theory of phasons in quasicrystals significantly contributes to this characteristic bias. It is shown that the most commonly used exponential Debye-Waller factor for phasons fails in the case of quasicrystals, and a novel method of calculating the correction factor within a statistical approach is proposed. The results obtained for model quasiperiodic systems show that phasonic perturbations can be successfully described and refinement fits of high quality are achievable. The standard Debye-Waller factor for phonons works equally well for periodic and quasiperiodic crystals, and it is only in the last steps of a refinement that different correction functions need to be applied to improve the fit quality.
authors.affiliation: Faculty of Physics and Applied Computer Science, AGH University of Science and Technology , Krakow, Poland.
authors.forename: Janusz
authors.initials: J
authors.lastname: Wolny
authors.affiliation: Faculty of Physics and Applied Computer Science, AGH University of Science and Technology , Krakow, Poland.
authors.forename: Ireneusz
authors.initials: I
authors.lastname: Buganski
authors.affiliation: Faculty of Physics and Applied Computer Science, AGH University of Science and Technology , Krakow, Poland.
authors.forename: Pawel
authors.initials: P
authors.lastname: Kuczera
authors.affiliation: Faculty of Physics and Applied Computer Science, AGH University of Science and Technology , Krakow, Poland.
authors.forename: Radoslaw
authors.initials: R
authors.lastname: Strzalka
keywords: Debye–Waller correction; average unit cell; phasons; quasicrystals; statistical methods