AB Polytypes

The purpose of this repository is to collect codes and data used in our paper "Bandgaps of long-period polytypes of IV, IV-IV, and III-V semiconductors estimated with an Ising-type additivity model".

Feel free to write to me (ramakrishnan@tifrh.res.in) for further information.

Codes

• hk2AB.ipynb converts hk sequences such as hh, kkk, khkh to the corresponding AB sequences AB, ABC, ABAC.
• AB2haegg.ipynb converts AB sequences such as AB, ABC, ABAC to the corresponding Haegg notation +-, +++, +--+.
• MakeGeoms.ipynb takes as inputs the stacking sequence (such as 'AB') and the elements ('Si' and 'C' for A and B) creates geometry.in for symmetry constrained geometry optimization using FHI-aims.
• DrawPolytypes.ipynb draws the structures of stacking arrangement of polytypes as viewed from the [10-10] plane of the hexagonal unit cell as shown in Fig. 1 of our paper.
• StoichiometricMatrix.ipynb creates the stoichiometric matrix used for ANNNI modeling. Each row corresponds to the terms in the Hamiltonian of a polytype. Columns correspond the the coefficient of J0, -J1, -J2, -J3, and -K of equation 4 of our paper. These coefficients (expect J0, which is 1 for all polytypes) are collected in Table II of our paper.
• Fit_ANNNI.ipynb fits Model-4 to HSE03 band gaps and prints the model parameters listed in Table V of our paper.

AB Polytypes dataset

FHI-aims input/output files 15 polytypes of 15 compositions are collected at https://doi.org/10.17172/NOMAD/2024.01.18-1

• PBE lattice optimization
• PBE, SCAN, HSE06 electronic band structures
• For SiC, additionally, phonon band structures at the PBE level are provided for the long polytypes 9R, 12R, 15R1, and 15R2

References

• Bandgaps of long-period polytypes of IV, IV-IV, and III-V semiconductors estimated with an Ising-type additivity model
  Raghunathan Ramakrishnan, Shruti Jain
  Journal of Chemical Physics, 159 (2023) 124702 (1-16).
  https://doi.org/10.1063/5.0166149
  See also the Supplementary materials (zip file)

@article{ramakrishnan2023bandgaps,
  title={Bandgaps of long-period polytypes of IV, IV-IV, and III-V semiconductors estimated with an Ising-type additivity model},
  author={Ramakrishnan, Raghunathan and Jain, Shruti},
  journal={The Journal of Chemical Physics},
  volume={159},
  number={12},
  year={2023},
  url={https://doi.org/10.1063/5.0166149},
  publisher={AIP Publishing}
}