  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.
