Conspicuous variation of the lattice unit cell in the pavonite homologous series and its relation with cation/anion occupational modulations

► Strong non-uniform variation of unit cell parameters in the pavonite homologous series. ► Conspicuous unit cell variation due to an underlying sub-lattice with cation/anion occupation. ► A modulated model common to the whole series using the superspace formalism proposed. ► Model successfully applied to the P7 pavonite Ag3(Bi,Pb)7S12. ► The model can be applied in a predictive way to other members of the family.