Interplay of B-Site Off-Centering and Molecular Orientations in the Mixed Hybrid Perovskite MAGe1xSnxI3
Abstract
B-site mixing is a common strategy for tuning properties of halide perovskites. In the lead-free system MAGe1-xSn_xI3, it brings tilting and off-centering into competition. Using large-scale molecular dynamics driven by a machine-learned interatomic potential, we map the structural behavior across the full composition range. MAGeI3 exhibits strong polar B-site off-centering that remains nearly constant up to the cubic transition, together with methylammonium (MA) orientational order that weakens progressively on heating. By contrast, MASnI3 combines octahedral tilting with weaker, predominantly antipolar off-centering. Ge-like behavior persists upon alloying and gives way to Sn-like behavior only beyond roughly 65 % Sn. In the high-temperature phases, the B-site cations remain locally off-centered but directionally disordered. On the Ge-rich side, the distorted inorganic framework biases the soft MA orientational landscape toward a restricted set of preferred directions. This coupling shows how the composition of the inorganic sublattice can tune molecular ordering in lead-free hybrid perovskites.
Related
- Interplay between photon condensation and electron-electron interactions in molecular systems
- Development and Testing of Tools for ORM Measurements and Quadrupole Centering
- Retrieval of multiple fibre orientations using X-ray dark-field signal modelling
- Orientations for skein-valued curve counting
- Extracting dipole orientations from asymmetric plasmonic nanostructures towards machine-learning-assisted spectropolarimetry
BibTeX
@misc{fransson2026interplay,
title = {{Interplay of B-Site Off-Centering and Molecular Orientations in the Mixed Hybrid Perovskite MAGe1xSnxI3}},
author = {Erik Fransson and Apinya Ngoipala and Oskar Öjstedt and Maths Karlsson and Paul Erhart and Julia Wiktor},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.03510},
eprint = {2609.03510},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.03510},
}
RIS
TY - UNPB
TI - Interplay of B-Site Off-Centering and Molecular Orientations in the Mixed Hybrid Perovskite MAGe1xSnxI3
AU - Erik Fransson
AU - Apinya Ngoipala
AU - Oskar Öjstedt
AU - Maths Karlsson
AU - Paul Erhart
AU - Julia Wiktor
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.03510
UR - https://arxiv.org/abs/2609.03510
AB - B-site mixing is a common strategy for tuning properties of halide perovskites. In the lead-free system MAGe1-xSn_xI3, it brings tilting and off-centering into competition. Using large-scale molecular dynamics driven by a machine-learned interatomic potential, we map the structural behavior across the full composition range. MAGeI3 exhibits strong polar B-site off-centering that remains nearly constant up to the cubic transition, together with methylammonium (MA) orientational order that weakens progressively on heating. By contrast, MASnI3 combines octahedral tilting with weaker, predominantly antipolar off-centering. Ge-like behavior persists upon alloying and gives way to Sn-like behavior only beyond roughly 65 % Sn. In the high-temperature phases, the B-site cations remain locally off-centered but directionally disordered. On the Ge-rich side, the distorted inorganic framework biases the soft MA orientational landscape toward a restricted set of preferred directions. This coupling shows how the composition of the inorganic sublattice can tune molecular ordering in lead-free hybrid perovskites.
ER -