Method of Pratt, Coyle and Ibers:

osf = overall scale factor
km = fractional contribution of twin domain m
Fcm = Fc of twin domain m

(n-1) of the fractional contributions can be refined.

TWIN r₁₁ r₁₂ r₁₃r₂₁ r₂₂ r₂₃ r₃₁ r₃₂ r₃₃ n

BASF k₂ k₃ ... k_n

or

MERG 0

BASF k₂ k₃ ... k_n

HKLF 5

C. S. Pratt, B. A. Coyle, J. A. Ibers,J. Chem. Soc. 2146, 1971

G. B. Jameson, Acta Crystallogr. A38,817, 1982