Structural, vibrational and quasiparticle properties of the Peierls semiconductor $\rm BaBiO_3$: a hybrid functional and self-consistent GW+vertex-corrections study

TL;DR

This study employs hybrid functionals and self-consistent GW methods with vertex corrections to accurately characterize the structural, vibrational, and electronic properties of the Peierls semiconductor BaBiO3, overcoming limitations of local density approximations.

Contribution

It demonstrates the effectiveness of hybrid functionals combined with advanced GW techniques in accurately modeling BaBiO3's properties, including charge disproportionation and bandgap.

Findings

Hybrid functionals accurately reproduce structural and electronic properties.

GW calculations confirm hybrid functional results but overestimate bandgap by ~0.4 eV.

Self-interaction errors in local functionals lead to inaccurate charge and bandgap predictions.

Abstract

$\rm BaBiO_3$ is characterized by a charge disproportionation with half of the Bi atoms possessing a valence 3+ and half a valence 5+. Because of selfinteraction errors, local and semi-local density functionals fail to describe the charge disproportionation quantitatively, yielding a too small structural distortion and no band gap. Using hybrid functionals we obtain a satisfactory description of the structural, electronic, optical, and vibrational properties of $\rm BaBiO_3$. The results obtained using GW (Green's function G and screened Coulomb potential W) based schemes on top of hybrid functionals, including fully selfconsistent GW calculations with vertex corrections in the dielectric screening, qualitatively confirm the HSE picture but a systematic overestimation of the bandgap by about 0.4 eV is observed.