Neutral and charged excitations in carbon fullerenes from first-principles many-body theories

TL;DR

This study evaluates the accuracy of first-principles many-body theories, specifically GW-BSE and QMC, in predicting electronic excitations of various carbon fullerenes, comparing results with experimental data to validate their effectiveness.

Contribution

It provides a comprehensive comparison of GW-BSE and QMC methods against experimental data for carbon fullerenes, establishing their reliability in nanoscale electronic property predictions.

Findings

Ionization potentials are accurately predicted across methods.

Electron affinities are high and size-independent.

Energy gap correlates with fullerene stability.

Abstract

We investigate the accuracy of first-principles many-body theories at the nanoscale by comparing the low energy excitations of the carbon fullerenes C_20, C_24, C_50, C_60, C_70, and C_80 with experiment. Properties are calculated via the GW-Bethe-Salpeter Equation (GW-BSE) and diffusion Quantum Monte Carlo (QMC) methods. We critically compare these theories and assess their accuracy against available photoabsorption and photoelectron spectroscopy data. The first ionization potentials are consistently well reproduced and are similar for all the fullerenes and methods studied. The electron affinities and first triplet excitation energies show substantial method and geometry dependence. These results establish the validity of many-body theories as viable alternative to density-functional theory in describing electronic properties of confined carbon nanostructures. We find a correlation between energy gap and stability of fullerenes. We also find that the electron affinity of fullerenes is very high and size-independent, which explains their tendency to form compounds with electron-donor cations.