Nonrad: Computing nonradiative capture coefficients from first principles

Mark E. Turiansky, Audrius Alkauskas, Manuel Engel, Georg Kresse, Darshana Wickramaratne, Jimmy-Xuan Shen, Cyrus E. Dreyer, Chris G. Van de Walle

Point defects in semiconductor crystals provide a means for carriers to recombine nonradiatively. This recombination process impacts the performance of devices. We present the Nonradcode that implements the first-principles approach of Alkauskas et al. (2014) [8] for the evaluation of nonradiative capture coefficients based on a quantum-mechanical description of the capture process. An approach for evaluating electron-phonon coupling within the projector augmented wave formalism is presented. We also show that the common procedure of replacing Dirac delta functions with Gaussians can introduce errors into the resulting capture rate, and implement an alternative scheme to properly account for vibrational broadening. Lastly, we assess the accuracy of using an analytic approximation to the Sommerfeld parameter by comparing with direct numerical evaluation.Program summaryProgram Title: NonradCPC Library link to program files:'s repository link: Ocean capsule: provisions: MIT LicenseProgramming language: Python 3Nature of problem: Nonradiative carrier capture at point defects in semiconductors and insulators significantly impacts the performance of devices. A first-principles approach to calculating nonradiative capture rates is necessary to guide materials design and provide atomistic insight into the nonradiative capture process.Solution method: Our code, written in the Python language, implements the first-principles methodology developed by Alkauskas et al. (2014) [8]. Nonradiative capture rates are calculated using a one-dimensional approach, which maps the prohibitively large phonon problem onto a single, effective phonon mode. Harmonic phonon matrix elements may then be computed using an analytic technique or by direct numerical integration of the harmonic oscillator wavefunctions. The electron-phonon coupling is evaluated using the VASP code [Kresse and Furthmuller (1996) [27]] to linear order for the effective mode. (C) 2021 Elsevier B.V. All rights reserved.

Computational Materials Physics
External organisation(s)
University of California, Santa Barbara, Center for Physical Sciences and Technology, U.S. Naval Research Laboratory, University of California, Berkeley, State University of New York, Stony Brook, Flatiron Institute
Computer Physics Communications
No. of pages
Publication date
Peer reviewed
Austrian Fields of Science 2012
103018 Materials physics
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