Modeling bismuth insertion in 1D hybrid lead halide TMSO(Pb x Bi y )I3 pseudo-perovskites

The structures of the disordered 1D (pseudo-)perovskites of general TMSO(Pb Bi )I formulation [TMSO = (CH)SO], obtained by doping the TMSOPbI species with Bi ions, are investigated through the formulation of a statistical model of correlated disorder, which addresses the sequences of differently occupied BI face-sharing octahedra (B = Pb, Bi or vacant site) within ideally infinite [(BI)] chains. The x-ray diffraction patterns simulated on the basis of the model are matched to the experimental traces, which show many broad peaks with awkward (nearly trapezoidal) shapes, under the assumption that the charge balance is fully accomplished within each chain. The analysis allowed to establish a definite tendency of the metal species to cluster as pure Pb and Bi sequences. The application of the model is discussed critically, in particular as what concerns the possibility that further B-site neighbors beyond the second may influence the overall B-site occupancies.