Upgrade to Pro — share decks privately, control downloads, hide ads and more …

ShakeNBreak: Identifying Ground-State Defect Structures (GRC 2022 Poster)

ShakeNBreak: Identifying Ground-State Defect Structures (GRC 2022 Poster)

Poster presented at the 2022 GRC Defects in Semiconductors conference, in New Hampshire, USA.

Code docs here: https://shakenbreak.readthedocs.io/en/latest/
Paper here: https://arxiv.org/abs/2207.09862

Other references:
Matter Preview of Defect Structure Searching: https://www.sciencedirect.com/science/article/pii/S2590238521002733
Metastable defects : https://doi.org/10.1039/D2FD00043A
Recombination at V_Cd in CdTe (case study): https://pubs.acs.org/doi/abs/10.1021/acsenergylett.1c00380

For other research articles and updates, check out my website at:

Seán R. Kavanagh

September 17, 2022

More Decks by Seán R. Kavanagh

Other Decks in Research


  1. Irea Mosquera-Lois,‡ Seán R. Kavanagh, ‡ Aron Walsh, David O. Scanlon
    Identifying the Ground State Structures of Point Defects in Solids
    Scan for the
    paper link and
    a slideshow
    I. Mosquera-Lois‡ & S.R. Kavanagh‡, A. Walsh, D.O. Scanlon, arXiv: 2207.09862 (2022)
    I. Mosquera-Lois & S.R. Kavanagh, Matter 4, 2602 10.1016/j.matt.2021.06.003 (2021)
    Arrigoni, M. & Madsen, G. K. H. npj Comp Mater 7, (1) 10.1038/s41524-021-00537-1 (2021)
    S.R. Kavanagh, D.O. Scanlon, A. Walsh, C. Freysoldt, Faraday Discuss. 10.1039/D2FD00043A (2022)
    Lany, S. & Zunger, A. Phys. Rev. Lett. 93, 156404 10.1103/PhysRevLett.93.156404 (2004)
    S.R. Kavanagh, A. Walsh, D.O. Scanlon, ACS Energy Lett. 6, 1392 10.1021/acsenergylett.1c00380 (2021)
    I. Mosquera-Lois‡ & S.R. Kavanagh‡, A. Walsh, D.O. Scanlon, JOSS (In Submission) (2022)
    The Problem: How prevalent are defect reconstructions?
    We see it in every material we investigated, including:
    , Si, ZnO, a-TiO2
    , r-TiO2
    , CdTe, GaAs, CeO2
    , Sb2
    , In2
    – Pretty prevalent!
    We find a range of physical origins for these reconstructions:
    Typical defect modelling approach:
    1. Create ‘ideal’ defect in host supercell on known crystal site.
    2. Gradient-based geometry optimisation.
    This initial configuration can reside in a local minimum on the potential
    energy surface as above for VCd
    in CdTe, yielding a metastable structure
    (Tetrahedral) instead of the true ground state arrangement (Te dimer).
    Standard defect supercell relaxation
    How important can it be?
    How can we obtain the correct defect structure?
    Reconstructions can drastically
    o Formation energies (ΔE>1 eV)
    o Concentrations
    o Transition levels
    o Recombination activity
    o Many other properties…
    a -> VSb
    formation energy
    diagram with the (metastable)
    results obtained using the
    standard supercell approach
    (dashed faded lines), and the
    correct ground states
    identified with our method
    (solid lines)
    b -> VSb
    energy level diagram
    c -> Corresponding structures
    We propose a method exploiting the localised nature of defect distortions
    and chemical intuition to efficiently navigate the potential energy surface.
    a b
    Standard defect calculations can
    yield incorrect structures
    Testing our approach on a range of diverse semiconductors and insulators (listed
    above), we find:
    o High prevalence of energy-lowering reconstructions for point defects, which are
    missed by standard defect calculations.
    o Robust performance (>95% success rate for all known cases)
    o Minimal additional computational cost, demonstrated by the range of materials
    and defects included in this study.
    o Using hybrid DFT with coarse numerical accuracy for expedient qualitative
    identification of defect reconstructions, followed by fully-converged calculations.
    Code openly-available at GitHub.com/SMTG-UCL/ShakeNBreak (Python & CLI)
    User-friendly, compatible with VASP, CASTEP, FHI-AIMs, Quantum Espresso, CP2K.
    @Kavanagh_Sean_ [email protected]

    View Slide