/polytype

A set of tools and structures for modelling perovskite polytypes

Primary LanguageJupyter NotebookMIT LicenseMIT

made-with-python License: MIT DOI

Perovskite Polytype Predictions

Polytypism, which is ubiquitous in oxide perovskites, also shows up in halide perovskites. Polytype structures have been experimentally observed using a variety of techniques and their influence on carrier performance has also been characterised (details can be found in the bottom reference papers). There are fascinating electronic and ionic phenomena to be expected in these materials.

Typical halide polytypes are illustrated here:

all_polytype_F1

This repository contains a set of tools and crystal structures for the description of perovskite polytypes in general, but halide perovskites in particular. We provide a combined method of Ising-type model Hamiltonian and genetic algorithm, which can be used to identify low energy configurations.

It is structured as follows:

Structure generator (Ji-Sang Park)

A python code to generate arbitrary perovskite stacking sequences to access complex polytypes and stacking faults.
Tips for generating the disp for any polytypes: compare the sequence with a perfect 3C structure, if the positions of both AX3 and B remain the same, then the index is (0, 0); for movement of AX3 and B, moving towards left (index + 1), moving towards right (index -1).

Structure analysis (Zhenzhu Li)

Scripts for electrostatic analysis.

Ising model / Genetic algorithm (Zhenzhu Li)

Python codes to search for high or low energy stacking sequences. See the IsingHamilotian_GA.ipynb file.

Picture 1

Structure collections

3D structure models that have been generated for various perovskites. They may be in VASP format (POSCAR) or Crystallographic Information File (CIF). Both can be opened using VESTA.

Requirements

The main language is Python 3 and has been tested using Python 3.6+. Basic requirements are Numpy and Scipy. pymatgen is also required for some of the tools.

Useful links

Used in