Energy decomposition analysis of neutral and negatively charged borophenes

TL;DR

This study uses first principles calculations to analyze how external negative charging affects the stability of borophenes, revealing preferences for certain charge states and the limitations of simple nearest-neighbour models.

Contribution

It provides a detailed energy decomposition analysis of charged borophenes, highlighting stability trends and the inadequacy of simple models for predicting binding energies.

Findings

Preference for borophene with very small or high negative charges.

Experimental structures like γ- and δ-sheets are energetically favored.

Nearest-neighbour models are too simplistic for accurate predictions.

Abstract

The effect of external static charging on borophenes - 2D boron crystals - is investigated by using first principles calculations. The influence of the excess negative charge on the stability of the 2D structures is examined using a very simple analysis of decomposition of the binding energy of a given boron layer into contributions coming from boron atoms that have different coordination numbers. This analysis is important to understand how the local neighbourhood of an atom influences the overall stability of the monolayer structure. The decomposition is done for the $\alpha$-sheet and its related family of structures. From this analysis, we have found a preference for 2D boron crystals with very small or very high charges per atom. The structures with intermediate charges are energetically not favourable. We have also found a clear preference in terms of binding energy for the experimentally seen $\gamma$-sheet and $\delta$-sheet structures that is almost independent on the considered excess of negative charge of the structures. On the other hand, we have shown that a model based solely on nearest-neighbour interactions, although instructive, is too simple to predict binding energies accurately.