STRENGTHENING OF QUARTET INVARIANT ESTIMATES VIA THE PRIOR ESTIMATION OF TRIPLET RELATIONSHIPS

Formulas for estimating quartet invariants depend on prior information on triplet invariants. If this coincides with the Cochran estimate then the classical quartet formulas [Hauptman (1975). Acta Cryst. A31, 680-687; Giacovazzo (1976). Acta Cryst. A32, 91-99, 100-104] are obtained. A mathematical theory is described that improves quartet estimates by exploiting some prior information on triplets. Special emphasis is devoted to the prior estimate of triplet invariants provided by the P10 formula.