Verification of first-principles codes: Comparison of total energies, phonon frequencies, electron-phonon coupling and zero-point motion correction to the gap between ABINIT and QE/Yambo

S. Poncé, G. Antonius, P. Boulanger, E. Cannuccia, A. Marini, M. Côté, X. Gonze

Research output: Contribution to journalArticlepeer-review

77 Citations (Scopus)

Abstract

With the ever-increasing sophistication of codes, the verification of the implementation of advanced theoretical formalisms becomes critical. In particular, cross comparison between different codes provides a strong hint in favor of the correctness of the implementations, and a measure of the (hopefully small) possible numerical differences. We lead a rigorous and careful study of the quantities that enter in the calculation of the zero-point motion renormalization of the direct band gap of diamond due to electron-phonon coupling, starting from the total energy, and going through the computation of phonon frequencies and electron-phonon matrix elements. We rely on two independent implementations: Quantum Espresso + Yambo and ABINIT. We provide the order of magnitude of the numerical discrepancies between the codes, that are present for the different quantities: less than 10-5 Ha per atom on the total energy (-5.722 Ha/at), less than 0.07 cm-1 on the Γ,L,X phonon frequencies (555-1330 cm-1), less than 0.5% on the square of the electron-phonon matrix elements and less than 4 meV on the zero-point motion renormalization of each eigenenergies (44-264 meV). Within our approximations, the DFT converged direct band gap renormalization in diamond due to the electron-phonon coupling is -0.409 eV (reduction of the band gap).

Original languageEnglish
Pages (from-to)341-348
Number of pages8
JournalComputational Materials Science
Volume83
DOIs
Publication statusPublished - 15 Feb 2014
Externally publishedYes

Keywords

  • Allen-Heine-Cardona theory
  • Density functional perturbation theory
  • Diamond
  • Electron-phonon coupling
  • Temperature dependence
  • Verification
  • Zero-point motion renormalization

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