Besides statistical and graphical measures, many structural features can be used to assess the quality of a Rietveld refinement. These include the metric symmetry of the lattice (which can assist in determining the true symmetry and in identifying isostructural compounds), bond distances and angles (which should fall within normal ranges), displacement coefficients, refined stoichiometry, the absolute values of the standard uncertainties of the fractional coordinates, the hydrogen bonding pattern, the presence of approximate symmetry, the presence of unindexed peaks in the pattern, and whether the refinement converges at all. Chemical knowledge can be built into a Rietveld refinement though the use of restraints and rigid bodies. A knowledge of chemical reasonableness proved important in refining the correct structures of [Fe(H2O)6](BF4)2, (Ba1.5Sr0.5)TiO4, and (Ba1.25Sr0.75)TiO4.
