The Ground State Electronic Energy of Benzene

TL;DR

This study evaluates various high-accuracy electronic structure methods for calculating the ground state energy of benzene, highlighting current challenges and providing benchmark data for future method development.

Contribution

It offers a comprehensive blind challenge assessment of multiple correlation methods for benzene's ground state energy, revealing their qualitative agreement and quantifying deviations.

Findings

Most methods estimate the FCI energy around -863 mE_H.

Root-mean-square deviation among methods is 1.3 mE_H.

Current methods face challenges extending to larger molecules.

Abstract

We report on the findings of a blind challenge devoted to determining the frozen-core, full configuration interaction (FCI) ground state energy of the benzene molecule in a standard correlation-consistent basis set of double-$\zeta$ quality. As a broad international endeavour, our suite of wave function-based correlation methods collectively represents a diverse view of the high-accuracy repertoire offered by modern electronic structure theory. In our assessment, the evaluated high-level methods are all found to qualitatively agree on a final correlation energy, with most methods yielding an estimate of the FCI value around $-863$ m$E_{\text{H}}$. However, we find the root-mean-square deviation of the energies from the studied methods to be considerable (1.3 m$E_{\text{H}}$), which in light of the acclaimed performance of each of the methods for smaller molecular systems clearly displays the challenges faced in extending reliable, near-exact correlation methods to larger systems. While the discrepancies exposed by our study thus emphasize the fact that the current state-of-the-art approaches leave room for improvement, we still expect the present assessment to provide a valuable community resource for benchmark and calibration purposes going forward.