New probabilistic formulas for finding the positions of correctly oriented atomic groups
Carmelo Giacovazzo · Acta Crystallographica Section A Foundations of Crystallography · 1988
The probabilistic procedure described by Main [In Crystallographic Computing Techniques (1976), edited by F. R. Ahmed, pp. 97-105. Copenhagen: Munksgaard] has been reconsidered. In polar space groups some primitive random variables (atomic positions or shift vectors for molecular fragments) may be conveniently restricted to regions which are smaller than a unit cell. This introduces two new expressions for triplet relationships; furthermore, a new type of phase relationship is introduced which is not equivalent to invariant and seminvariant relationships.