On the reliability of the Σ₂ relation. II. Artificial structures in P2₁/c

It is shown that for structures in which the coordinates of atoms have been randomly generated, the probability formula gives an underestimate of the experimental probability of the Σ₂ relation. Concentration of atoms in planes increases the number of reliable triplet sign relations. Although the presence of a non-crystallographic centre of symmetry results in a larger number of triplet relations with high E_HE_KE_{H - K} values, the percentage of failures is increased compared with random structures.