Ichak rentgenografiyasi: natijani ko'rsatadigan tayyorgarlik

Buzuqlik

Asosiy maqola: crystallographic disorder
A common challenge in refinement of crystal structures results from crystallographic disorder. Disorder can take many forms but in general involves the coexistence of two or more species or conformations. Failure to recognize disorder results in flawed interpretation. Pitfalls from improper modeling of disorder are illustrated by the discounted hypothesis of bond stretch isomerism.^[132] Disorder is modelled with respect to the relative population of the components, often only two, and their identity. In structures of large molecules and ions, solvent and counterions are often disordered.

Applied computational data analysis

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The use of computational methods for the powder X-ray diffraction data analysis is now generalized. It typically compares the experimental data to the simulated diffractogram of a model structure, taking into account the instrumental parameters, and refines the structural or microstructural parameters of the model using eng kichik kvadratchalar based minimization algorithm. Most available tools allowing phase identification and structural refinement are based on the Rietveld usuli,^[133][134] some of them being open and free software such as FullProf Suite,^[135][136] Jana2006,^[137] MAUD,^{[138][139][140]} Rietan,^[141] GSAS,^[142] etc. while others are available under commercials licenses such as Diffrac.Suite TOPAS,^[143] Match!,^[144] etc. Most of these tools also allow Le garov refinement (also referred to as profile matching), that is, refinement of the cell parameters based on the Bragg peaks positions and peak profiles, without taking into account the crystallographic structure by itself. More recent tools allow the refinement of both structural and microstructural data, such as the FAULTS program included in the FullProf Suite,^[145] which allows the refinement of structures with planar defects (e.g. stacking faults, twinnings, intergrowths).