NMR shifts for polycyclic aromatic hydrocarbons from first-principles

TL;DR

This paper uses first-principles density-functional theory to calculate NMR chemical shifts in polycyclic aromatic hydrocarbons, from benzene to graphene, achieving good agreement with experimental data and revealing size-dependent trends.

Contribution

It introduces a novel approach combining orbital magnetization theory with NMR calculations to accurately predict chemical shifts in large aromatic systems.

Findings

Good agreement with experimental NMR shifts

Characterization of chemical shift trends with system size

Method applicable to infinite graphene structures

Abstract

We present first-principles, density-functional theory calculations of the NMR chemical shifts for polycyclic aromatic hydrocarbons, starting with benzene and increasing sizes up to the one- and two-dimensional infinite limits of graphene ribbons and sheets. Our calculations are performed using a combination of the recently developed theory of orbital magnetization in solids, and a novel approach to NMR calculations where chemical shifts are obtained from the derivative of the orbital magnetization with respect to a microscopic, localized magnetic dipole. Using these methods we study on equal footing the $^1$H and $^{13}$C shifts in benzene, pyrene, coronene, in naphthalene, anthracene, naphthacene, and pentacene, and finally in graphene, graphite, and an infinite graphene ribbon. Our results show very good agreement with experiments and allow us to characterize the trends for the chemical shifts as a function of system size.