Computational Strategy for Graphene: Insight from Odd Electrons Correlation

TL;DR

This paper explores the significant role of odd electron correlation in graphene, proposing computational strategies using unrestricted Hartree-Fock and DFT methods to analyze magnetic, reactive, and mechanical properties.

Contribution

It introduces a practical computational approach employing unrestricted Hartree-Fock theory to study electron correlation effects in graphene and nanographenes.

Findings

Unrestricted Hartree-Fock can quantify electron correlation in graphene.

Electron correlation influences magnetism, reactivity, and mechanical properties.

Deformation of the carbon skeleton can control electron correlation.

Abstract

The correlation of odd electrons in graphene turns out to be significant so that the species should be attributed to correlated ones. This finding profoundly influences the computational strategy addressing it to multireference computational schemes. Owing to serious problems related to the schemes realization, a compromise can be suggested by using single-determinant approaches based on either Hartree-Fock or Density-Functional theory in the form of unrestricted open-shell presentation. Both computational schemes enable to fix the electron correlation, while only the Hartree-Fock theory suggests a set of quantities to be calculated that can quantitatively characterize the electron correlation and be used for a quantitative description of such graphene properties as magnetism, chemical reactivity, and mechanical response. The paper presents concepts and algorithms of the unrestricted Hartree-Fock theory applied for the consideration of magnetic properties of nanographenes, their chemical modification by the example of stepwise hydrogenation, as well as a possible governing the electron correlation by the carbon skeleton deformation.