2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/106960Diffracted X-ray waves in crystals have relative phases regarding the mathematical format used to describe them. A forward propagating wave can be defined with either negative or positive time evolution, i.e. kr - wt or $wt - kr. Physically measurable quantities are invariant with respect to the choice of definition. This fact has not been clearly emphasized neither extensively explored when deriving well-established equations currently being used in many X-ray diffraction related techniques. Here, the most important equations are generalized and consequences of conflicting undertaken definitions discussed.5 pages, 3 figuresMaterials Sciencetext