checkCIF procedure
PLAT230
PLAT230 Type_2 Hirshfeld rigid-bond test [Acta Cryst. (1976), A32, 239-244]
The components of the anisotropic displacement parameters along chemical bonds are assumed to be equal in magnitude. Large differences might indicate contamination of these parameters with other (unresolved) effects such as (substitutional) disorder, model or data errors and/or over-refinement. Atomic sites assigned the wrong scattering type (e.g. Ag versus Br) should generate 'problem signals' with this test. Data sets corrected for absorption effects with DELREF techniques (e.g. DIFABS, SHELXA, XABS2) often show large DELU values for bonds involving the heaviest atom. Note: The original 'Hirshfeld-test' was defined in absolute terms (see F.L.Hirshfeld, Acta Cryst. (1976). A32, 239-244). The current test is with reference to the associated standard uncertainty.