Percolation of In(III) in mixed perovskites of (PCA)₂Cu(II)Cl₄ and (PCA)₄Cu(I)In(III)Cl₈

Emergent electronic behavior has been demonstrated in the mechanochemical synthesis of mixtures of two-dimensional mixed-valence transition-metal halide perovskites. Pressure drives intervalence charge transfer and electronic conductivity in Cu(I)-Cu(II)-In(III) chloride perovskites within a p-chloroanilinium organic framework. A steric, space-filing packing model has been proposed to understand the favorable packing of Cu(I), Cu(II), and In(III) at 25% In molar fraction [1,2]. In this work, we formulate an electrostatic model to accurately predict percolation of In(III) in Cu(I)-Cu(II)-In(III) chlorides as a function of temperature and In concentration. A first-principles cluster expansion-Monte Carlo approach is implemented to predict the energetics at finite temperature, while a percolation model is then applied to extract the threshold and identify Cu(I)-In(III) clusters with increasing In concentration. This model connects the local electron spin structure with localized Jahn-Teller distortions and conductivity.

References

[1] Li, J. et al. Angew. Chem. Int. Ed. 62, e202300957 (2023).

[2] Connor, B. A. et al. Chem. Sci. 12, 8689-8697 (2021).