Efficient calculation of van der Waals dispersion coefficients with time-dependent density functional theory in real time: application to polycyclic aromatic hydrocarbons

TL;DR

This paper presents a real-time TDDFT-based method to efficiently compute van der Waals dispersion coefficients for large polycyclic aromatic hydrocarbons, enabling scalable and accurate ab initio calculations.

Contribution

It introduces a novel real-time TDDFT approach for calculating dispersion coefficients that scales favorably with molecular size and can be extended to higher-order coefficients.

Findings

Successfully computed C6 coefficients for PAHs up to C66H20

Demonstrated favorable scaling with system size

Method applicable to higher-order van der Waals coefficients

Abstract

The van der Waals dispersion coefficients of a set of polycyclic aromatic hydrocarbons, ranging in size from the single-cycle benzene to circumovalene (C66H20), are calculated with a real-time propagation approach to time-dependent density functional theory (TDDFT). In the non-retarded regime, the Casimir-Polder integral is employed to obtain C6, once the dynamic polarizabilities have been computed at imaginary frequencies with TDDFT. On the other hand, the numerical coefficient that characterizes the fully retarded regime is obtained from the static polarizabilities. This ab initio strategy has favorable scaling with the size of the system - as demonstrated by the size of the reported molecules - and can be easily extended to obtain higher order van der Waals coefficients.