A new potential for methylammonium lead iodide.

We present a new set of interatomic potentials for modelling methylammonium lead iodide. The potential model uses existing potentials for lead iodide and methylammonium, and new functions are fitted to enable these pre-existing potentials to be used together, while still being capable of modelling lead iodide and methylammonium iodide as separate materials. Fitting was performed using a combination of ab initio and experimental reference data. Our simulations are in agreement with experiment and reveal the short and long range ordering of the molecular cations and lead iodide octahedra.